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Stars and Stripes, Justice Dept. Washington, D.C.  Photo © 2007 Scott Hanley

The Structure and Functions of Congress,            Part 1: Structure (.pdf)


This chapter considers how Congress is structured, both in its division into two equal chambers that must agree with each other to pass legislation, and within each chamber, where three particular structures shape the functioning of each chamber: the leadership structure, the committee structure, and the structure of log-rolling and vote-trading.

Learning Objectives: In this chapter you should learn the following:

1. What type of bicameral structure Congress has, why, and its effects on policymaking;

2. The functional structures of Congress, including

a. the leadership structure;

b. the committee structure;

c. the vote-trading (logrolling) structure;

3. The roles of the different leadership positions;

4. What veto power is (also known as gatekeeping power) and what (and who) are veto players;

5. What agenda control is, and why it matters;


The structure of Congress has two dimensions. The first dimension is the constitutionally structured division of Congress into two separate chambers—House and Senate—which is partly a division of labor, but mostly a duplication of labor, as we will see soon. The second dimension is the internal functional structure of each chamber, which is in a small part constitutionally required, but which mostly is a matter of rules created by the chambers themselves for functional convenience. As we’ll see, because of the duplication of labor, the two chambers have similar functional structures.

1. The Constitutional Division of Legislative Power into Two Chambers

Key Concepts

Why the Framers created two chambers of Congress

All legislative powers herein granted shall be vested in a Congress of the United States, which shall consist of a Senate and House of Representatives (U.S. Constitution, Article 1, §1).

The Constitution requires that the American federal legislature—the Congress—be composed of two chambers, a House of Representatives and a Senate. This bicameral structure (bi meaning “two,” and camera meaning “chamber”) was chosen to serve two purposes: 1) satisfying the states’ conflicting demands for representation and 2) further fragmenting the political power of the federal government in order to constrain it.

There are 3 types of legislative structures:

1. Unicameralism: Only one house in the legislature (uni = “one,” as in unicycle, camera = “chamber”). About half the world’s countries use unicameral governments. Examples include the Japanese Diet and the New Zealand Parliament, as well as the Nebraska state legislature (the only unicameral state legislature in the U.S.).

2. Assymetrical Bicameralism: Two houses in the legislature (bi = “two” as in bicycle), which are assymetrical because one has substantially more legislative authority than the other. Usually the lower house (such as Britain’s House of Commons) has legislative authority, and the upper house (such as Britain’s House of Lords) has very little authority. Another country with an assymetric bicameral legislature is Canada.

3. Symmetric bicameralism: Two houses, each with roughly equal legislative authority.

These different structures have different effects on legislative efficiency. The unicameral structure allows legislation to pass quickly, as only one chamber’s agreement is necessary. The asymmetric bicameral structure also usually allows legislation to pass quickly, because the upper house generally has little authority to block legislation. But the symmetric bicameral system, of the U.S. is a design that intentionally complicates the legislative process by requiring two chambers to agree on laws, not just in general, but in every detail.

Beyond ensuring each state at the Constitutional Convention had sufficient representation, a major purpose of this structure was to prevent congressional tyranny, by making it harder to act swiftly, without sufficient thought or without being effectively challenged. Just as the Framers fragmented political power by first dividing it between the states and the federal government, and second by dividing the federal government into three branches, the bicameral structure of the U.S. Congress is a third fragmentation of political power. Because the two chambers have equal legislative authority, they are symmetrical in power, and we call the structure symmetrical bicameralism.

James Madison explains this purpose in Federalist 51.


A dependence on the people is, no doubt, the primary control on the government; but experience has taught mankind the necessity of auxiliary precautions… In republican government, the legislative authority necessarily predominates. The remedy for this inconveniency is to divide the legislature into different branches; and to render them, by different modes of election and different principles of action, as little connected with each other as the nature of their common functions and their common dependence on the society will admit.

Americans often complain about “gridlock” in government, but gridlock is the cost the Framers purposely accepted in order to ensure the benefit of non-tyrannical government. As software engineers say, it’s a feature, not a bug. The Framers were not certain that having to face regular elections (“a dependence on the people”) was a sufficient protection against a tyrannical legislature, so they purposely divided it in order to obstruct its efficiency.

This obstruction lies in the constitutional requirement that each Chamber has to approve a bill before it can be sent to the President to either become law or be vetoed. This—both chambers having authority to write laws, but only with the other chamber’s agreement—is where the chambers have a duplication of labor. Instead of requiring only a single majority, in one of the chambers, to approve of bills, two separate majorities must be achieved, and both must approve of precisely the same wording in the bill—any difference in wording means they must resolve the difference and each chamber must once again muster a majority in support of the bill. The purpose of this is that if one chamber proposes a law that is beyond its authority, or abusive of the rights of the people, the other chamber will, or at least should, refuse to agree to the bill.

Americans have a complicated view of Congress. In part they tend to revere the Constitution, and the intent of the Framers to prevent tyranny, so most people do not question the Constitutional design of the Congress. At the same time public frustration with congressional gridlock is an on-going complaint. In 2013 public approval of Congress dropped to a low of 9%. This confusion of liking the system, but disliking the results it produces reveals confusion in Americans’ understanding of their own political system. First, people tend to think the system works well when it obstructs legislation they don’t like, while disliking the system when it obstructs legislation they do like. But the system was not designed to only create roadblocks for one group’s proposals, but as a way for any proposal to undergo extensive scrutiny and possibly be blocked—even when a policy you fervently support is blocked, the system is working as intended.

Second, when people object to gridlock their overall belief in the American political system leads them to blame the actors within the system—Congressmembers—instead of the system itself. To some extent this is legitimate, but the type of people who get into the system, who become Congressmembers, is still a consequence of the American system, the electoral part. Change our electoral system and we will get, to some extent, a different type of person in office. But even a different type of people will be operating within the same system. Politics will still be in part a conflict over what type of policies we should enact, and the actors will still use the same means available within the system to block policies they don’t like.

In short, if we really like the American political system of symmetric bicameralism, we need to recognize that gridlock is part of the designed intent of the system. But if we think gridlock is a problem, the problem is in the system, not in the people working within it.

The Necessity of Compromise

A second effect of the requirement that both branches agree to all the specific details of laws is that lawmakers are usually forced to compromise. Most often, supporters of a policy do not get everything they want, but have to accept some compromises in order to build a majority in support of legislation and overcome opposition. This is true whether we focus on the individual Congressmembers who support a particular policy or whether we consider the party that is in power. It is particularly true in the Senate, in which the rules allow the minority greater ability to obstruct legislation through the use of the filibuster, as we will see in the chapter on the legislative process.

This compromise means American public policy tends to take much longer to enact, to be more centrist, often more muddled and less coherent, and not fully satisfying to anyone, but it does tend to prevent radical policy changes. The history of the effort to create a national health care system provides a good example.

1945: Just months after the end of WWII President Truman becomes the first U.S. President to propose a national health care system, but is unsuccessful.

1965: 20 years later President Johnson signs into law Medicare and Medicaid. Although Johnson declared that the idea “all started with the man from Independence,” Missouri (Truman), these programs do not cover all Americans, just those over 65 (Medicare) and those who are poor and/or disabled (Medicaid), and they are not fully government-run, but work in coordination with private insurers.

1976: A decade later President Carter proposes a national health care system with universal coverage for all Americans, but the legislation never passes Congress, although his party has a majority in both chambers.

1993: Two decades later, President Clinton proposes a national health care system, but as with Carter, despite his party having a majority in both chambers of Congress, the legislation does not pass.

2010: Almost another two decades later, 65 years after Truman’s first proposal, Congress passes “Obamacare” (more properly, PPACA, the Patient Protection and Affordable Care Act, often called just ACA). For the first time, all Americans are guaranteed health insurance, but the law still does not create a true national health care program, because instead of health care coverage being granted to all Americans through a government-run insurance plan, all Americans are mandated by law to buy insurance through private companies.

The point of this story is the same, regardless of whether or not one supports nationalized health care. The effort to create national health care in the U.S. has taken more than half a century, as opponents have consistently been able to use the structure of Congress to block it, and even today with the Affordable Care Act extending health insurance coverage to all Americans, the law is a compromise product, working through private health insurers rather than replacing them with a government program.

Politics has been called “the art of compromise,” and the American political system effectively has that definition build into it (the Constitution itself is imbued with a great number of compromises). While some people praise compromise as a noble act of statesmanship, as often as not it is just pragmatic political strategy. Others denounce compromise as selling out, failing to recognize that the American system was purposely designed to prevent any one group’s policy preferences from completely dominating everyone else’s preferences, as emphasized by James Madison in Federalist 10.

Among the numerous advantages promised by a well-constructed Union, none deserves to be more accurately developed than its tendency to break and control the violence of faction… [of] a number of citizens, whether amounting to a majority or minority of the whole, who are actuated by some common impulse of passion, or of interest, adverse to the rights of other citizens…

Gridlock, compromise, and preventing anyone from getting their way entirely, are the characteristics—the intended characteristics—of the American political system.

2. The Internal Functional Structure of the Two Chambers

Key Concepts

Internally, both the House and the Senate have three sets of structures that shape how they function. Two of these are formal structures: the leadership structure and the committee structure. The third is an informal structure: logrolling and vote-trading.

2.1  The Leadership Structure

The first of the formal internal structures of the House and Senate (and by formal we mean official and defined by written rules) are the chambers’ leadership structures. The House and Senate both have leadership structures that are based on party lines, although the Constitution makes no mention of parties, and the Framers did not anticipate or intend for the chambers to have party divisions. We will first discuss the House, then the Senate.

The House of Representatives Leadership Structure

“The House of Representatives shall choose their speaker and other officers” (U.S. Constitution, Article 1, §2, paragraph 5).

1. Speaker of the House

The only constitutionally required leadership position in the House is the Speaker of the House, who is officially the presiding officer of the House of Representatives. Because the Framers did not anticipate the rise of political parties, the Speaker is theoretically the head of the whole House, and in fact does operate that way to a certain extent, being the chief organizer of the House’s legislative process. But in practice, both parties nominate candidates to be Speaker, and of course the candidate for the majority party wins, so the Speaker primarily represents his/her own party. (The real battle for Speaker may occur within the majority party, as rivals contend for their party’s nomination.)

The Speaker has extensive power, which includes.

i. Influence in committee assignments and committee chairmanships for his party’s Congressmembers. Congressmembers care deeply about which committees they sit on, both because they wants to deal with legislation they care about and because they want to sit on committees that matter to their constituents. A Representative from a rural area, for example, may want to sit on the Agricultural Committee, while a veteran may want to sit on the Armed Services Committee. Within limits, the Speaker has the opportunity to wield power by rewarding or punishing members of his party. The Speaker also appoints a majority of the members of the all-important House Rules Committee, which sets the rules for final debate on all legislation, and members of special “Select” committees (that deal with topics of special significance) and conference committees, the ones that meet with members of the Senate to resolve differences in legislation passed by both chambers.

ii. Assigning bills to committee. As we will see below, committees are of fundamental importance in Congress, and some bills could be assigned to either one committee or another. Since one committee may be more favorable toward the bill, while the other may decide to bury the bill, the Speaker can influence the fate of legislation, possibly killing it, simply by her choice of which committee to assign it to. This effective power to stop legislation in its tracks is called veto power, and the Speaker is a veto player, one who has the ability to wield veto power. Such power can also be thought of as gatekeeping power—the Speaker can open the gate and help a bill go through, or she can shut the gate and keep the bill from going any further.

iii. Scheduling bills for a vote on final passage. Nearly all bills get voted on multiple times throughout the legislative passage, but the vote on final passage is the vote that determines whether the chamber as a whole passes the bill or not. The Speaker is the one who determines when this vote occurs, which allows them to 1) delay a vote indefinitely, so that perhaps it never passes (which can only occur if there is not very strong demand in his party to pass the bill); 2) delay a vote temporarily while he rounds up enough votes in his party to get it passed; or 3) to rush a vote through quickly before others can organize effective opposition to it.

Speakers rarely schedule a bill for a vote on final passage until they are confident they have enough votes to pass it. Occasionally, however, they fail, as happened several times to Republican Speaker of the House John Boehner, who has had trouble controlling hard-line conservative “Tea Party” Republicans. In June 2013, for example, he lost a vote on a farm bill because of cuts to the Food Stamps welfare program: some Democrats voted against it because of the cuts, which Boehner expected, but some Tea Party Republicans also voted against it because they thought the cuts did not go far enough.

Above all else, Speakers try to ensure party discipline, having all members of the party following the party leadership’s lead. While party discipline is normally much stronger in the House than the Senate, it cannot always be achieved. While Speakers are supposed to coordinate the legislative activities of their party, that can be difficult when they are in conflict with their own party’s members, because they have few real means of control over those members. In the end, each Representative is accountable not to their party’s leadership, but to their own constituency. Party leadership can determine a Representatives’ committee assignments, they can provide assistance or obstruction to a Representative’s legislative efforts, and they can provide assistance (or not) in their re-election efforts, but they cannot directly command them and order them to vote a particular way. And sometimes party leadership can only lead by rushing to get in front of wherever the members of their party have already decided they are going.

iv. Leader of the Loyal Opposition. When the Speaker and the President are of different parties (a situation we call divided government), the Speaker is the highest ranking official of the party in opposition to the President. When the Speaker and President are of the same party, the Speaker may see her duty as helping to successfully shepherd the President’s legislative agenda through the House. But when they are of opposite parties, the Speaker may see her role as obstructing the President’s legislative goals.

The concept of a “loyal opposition” is an important one, as it emphasizes that the opponents of the President are not disloyal, because their proper loyalty is to the country, rather than to its chief executive. Although the concept is used more often in parliamentary systems, it is also appropriate to the U.S.

v. Finally, the Speaker of the House is second in line of the succession for the presidency (behind the Vice President). That is, if both the President and the Vice President resign, are removed, or die (or some combination thereof), the Speaker will become the President. This position comes from Article 2, §1, paragraph 6 of the Constitution, which authorizes Congress to

by Law provide for the Case of Removal, Death, Resignation or Inability, both of the President and Vice President, declaring what Officer shall then act as President.

Congress has done so in the Presidential Succession Act of 1947, and various amendments to the Act since then.

2. The House Majority (and Minority) Leader and the Majority (and Minority) Whips

Although the Constitution only requires a Speaker of the House, it allows the House to “choose…their other officers, whichever ones they decide they need. And they do need other officers, because their business is complex, and it requires a tremendous amount of work to coordinate their own party so that it can be effective when it comes into conflict with the other party. And as previously noted, although the Speaker is always the leader of the majority party, constitutionally the position is the leader of the whole House. The rest of the leadership structure is explicitly along party lines, and both the majority and minority parties have identical leadership structures.

Each party has an official leader. The leader of the party that holds more seats in the House is the Majority Leader, and the leader of the party with fewer seats is the Minority Leader. There is a difference between the two, though, because the Minority Leader is the top official of his party, and is the one who is in line to become Speaker if his party gains a majority. In this sense, the Minority Leader can be understood as a “shadow Speaker,” the minority party’s counterpart to the Speaker of the House. The Majority Leader is actually her party’s second most important leader, because her party also holds the House Speakership.

The role of the party leader is to manage the party’s legislative business and try to ensure support among the party’s members in the House for proposals supported by the party leaders. In this, the Majority Leader can be understood as assisting the Speaker of the House.

Both parties also have a “Whip,” who helps the party leaders round up votes for their party’s positions, whether in support of a bill or in opposition to it. In other words, their job is to ensure party discipline. The term comes from fox hunting, where the job of the “whipper in” is to keep the dogs together in a pack, and keep them from wandering off. That is, the job of party Whip is to keep your party’s legislators in a unified pack, and keep them from wandering off to cast votes against the party leaders, or to fail to vote when their vote is needed to pass, or block, a bill.

The Senate Leadership Structure

“The Vice President of the United States shall be President of the Senate, but shall have no vote, unless they be equally divided.

The Senate shall choose their other officers, and also a President pro tempore, in the absence of the Vice President, or when he shall exercise the office of President of the United States” (U.S. Constitution, Article 1, §3, paragraphs 4-5).

As with the House, the Senate’s constitutionally required leadership positions are theoretically not party-based, but in reality all the leadership authority is based on the party structure. Unlike the Speaker of the House, though, these constitutionally required leadership positions wield little real power.

1. President of the Senate

We can cover the Senate Leadership structure much more quickly, because so much of it is just like the House leadership structure. But there are a few important differences. First, the Senate has no Speaker, nor any constitutionally required role that is the equivalent of the Speaker. The Vice President of the United States is designated as the President of the Senate, but the only authority given is to cast tie-breaking votes, which happens only rarely. So Vice Presidents rarely bother to preside over the Senate unless a tie-vote on important legislation seems likely or on ceremonial occasions.

2. President Pro Tempore

The Constitution also requires a President Pro Tempore, to preside over the Senate when the Vice President is not in attendance (which is most of the time). The President Pro Tempore is normally the longest serving senator in the majority, but the position is largely ceremonial, and majority party Senators take turns serving as the presiding officer on a daily basis.

In brief, the two constitutionally required officers of the Senate rarely play a significant role in the Senate’s legislative activities.

3. The House Majority (and Minority) Leader and the Assistant Majority (and Assistant Minority) Leaders

Just as with the House, the parties in the Senate have Leader and Whip positions, although in the Senate the Whips are technically known as the Assistant Part Leader. The real leader of the Senate—to the extent the Senate can be said to have leadership—is the Senate Majority Leader. Like the Speaker of the House, the Senate Majority Leader manages the flow of legislation, and tries to ensure that his party’s bills come to a vote on final passage only when there are sufficient votes to pass it. The Senate Majority Leader also plays similar roles in influencing committee assignments and determining to which committee bills are submitted, with similar (although weaker, veto power).

Senators are more elite than Representatives, though, and do not care to be led. Consequently, party discipline in the Senate is normally much weaker than in the House, and Party Leaders may be chosen by their parties as much for their lack of ability to command as for any actual leadership qualities. This does not mean Senate Majority Leader is not an important position, just that it is a position in which it is difficult to exercise strong leadership over one’s own party members.

2.2  The Committee System

Each House may determine the rules of its proceedings (U.S. Constitution, Article 1, §5, paragraph 2)

The second of the formal internal structures of the House and Senate are the chambers’ committee systems. The day to day legislative work in both chambers occurs not on the floor of the chamber with all members in attendance, but in smaller rooms where an individual committee is considering a bill. Nothing in the Constitution requires committees, but neither chamber could operate effectively without them.

Each committee has a specific jurisdiction. The House Finance Committee, for example, has jurisdiction over banks, economic stabilization, insurance, international financial and monetary organizations, and securities and exchanges, among a variety of other issues. By contrast, the House Agricultural Committee has jurisdiction over agriculture in general, agricultural and industrial chemistry, stabilization of prices of agricultural products, crop insurance, soil conservation, forestry, rural electrification, and livestock inspection, among other issues. This specialization allows the House to work on multiple issues simultaneously.

As noted above when discussing the Speaker of the House, every bill submitted by a member of the House is assigned to a committee, as determined by the Speaker. The different jurisdictions of the committees provide some guidance to the Speaker’s choice, but because many political issues are complex, there are issues on which multiple committees have overlapping and competing jurisidiction. The war and foreign policy blog “War on the Rocks” provides an example.

Examples of the jurisdictional overlap: the House Committee on Homeland Security and Senate Homeland Security and Government Affairs Committee have jurisdiction over the physical aspects of border security; the Judiciary committees oversee enforcement of immigration law; the House Committee on Homeland Security and Senate Homeland Security and Government Affairs Committee are responsible for transportation security, but the Transportation committees have jurisdiction over transportation safety.

It is this jurisdictional overlap that gives the Speaker of the House some freedom of choice in determining where to assign a bill, with the expectations of being able to count on a committee chairman to shepherd through a bill the Speaker likes or to go slow on a bill the Speaker doesn’t like. It doesn’t always work, but the Representative who proposes a bill doesn’t even have that much control over it once submitted.

Every committee includes a set of subcommittees, each of which is also jurisdictionally specialized, focusing only on a subset of the committee’s jurisdiction. For example, the Senate Committee on Environment and Public Works has the following subcommittees:

Everything that we have said of committees applies to subcommittees as well. Bills that are assigned to a committee are normally then assigned to a subcommittee. And just as the Speaker has some freedom of action in determining to which committee to assign a bill, the committee Chair has some freedom of action in determining to which committee to assign a bill, and to some extent the subcommittee chair has agenda control power, the capacity to put bills near the top of the agenda or to bury them down at the bottom. Because thousands of bills are submitted in each session of Congress, while each committee and subcommittee can only work on a few bills at a time, most bills end up dying in committee without ever having been seriously addressed.

Because the House and Senate have a duplication of labor on legislative responsibilities, their committee systems are very similar. However because there are fewer Senators than Representatives, each Senator normally serves on more committees than does each Representative.

Most committees’ jurisdiction also includes oversight over specific executive branch agencies, as discussed below in the section on the functions of Congress.

The Importance of Committee Chairs

The chairmanship is a powerful position, because the chair controls the process of legislation within the committee, and nearly all bills must go through a committee, and be approved by them, before they have an opportunity to be voted on for final passage. The most important power of the committee chair is agenda control, the ability to move a bill forward on the agenda or push it to the back of the agenda. Imagine yourself as a committee chair, and two people make proposals, one of which you like a lot, and the other which you think is awful. As committee chair, you have the power to determine which one of these will get placed near the front of the committee’s agenda, and which will get buried so far to the back of the agenda that your committee will likely never deal with it. Agenda control is another example of veto, or gatekeeping, power, and committee chairs are important veto players in the legislative process.

The minority party has a “shadow chair,” who is called the “ranking member.” If the party gains a majority in the House, this person normally becomes the chair. This person is responsible for organizing opposition—to the extent possible when the other party has an absolute majority—to committee bills that are opposed by his party.

Committee chair positions are vitally sought after by Congressmembers. In addition to the desire to be powerful and influential, committee chairmanships are a matter of prestige (particularly the committees seen as especially important, such as the Committee on Intelligence, which oversees the executive branch intelligence agencies), and they can put the member in a position to provide great benefit to their constituents, whether by ensuring bills are designed in ways that promote their constituents interests or by ensuring federal money flows to their district for various projects. The position also enables the chair to build support from other members by doing the same for their districts.

2.3  The Informal System of Vote Trading

Not all structures are formal. Some are informal, which means they are not written down and officially enforced. This does not mean they are any less important, as anyone who breaks a social norm and suffers social retribution in response finds out. In both chambers of Congress, there is an important informal system of vote trading, exchanging votes on other members important items of legislation.

In Congress, this system is often called “logrolling.” The idea is that no-one can roll a large log by himself, but if several work together they can easily do so. Of course once I help you roll your log, you owe me help with my log. Or, if I vote for your bill, you owe me a vote on my bill.

This can work in two ways. One is to explicitly trade votes on different items of legislation, as explained by economist William Shughart.

The logic of collective action explains why farmers have secured government subsidies at the expense of millions of unorganized consumers, who pay higher prices for food, and why textile manufacturers have benefited significantly from trade barriers at the expense of clothing buyers. Voted on separately, neither of those legislatively enacted special-interest measures would pass. But by means of logrolling bargains, in which the representatives of farm states agree to trade their votes on behalf of trade protectionism in exchange for pledges of support for agricultural subsidies from the representatives of textile-manufacturing states, both bills can secure a majority.  

Another way is to implicitly trade votes on a single item of legislation, by allowing various members to attach amendments that provide particular benefits to their constituents, what is called legislative pork. Allowing you to do so buys your vote on the bill, and allowing me to do so buys my vote on the bill. And even if I do not like your pork I’m willing to vote for it by voting “yes” on the whole bill because it includes my pork. And even if you don’t like my pork, you vote yes for exactly the same reason.

The public generally does not like to hear that Congress operates this way, thinking that Congressmembers ought to vote based on the merits of a bill. But in the big picture of U.S. government spending, the pork that is produced by such logrolling is minor, and it is the grease that keeps the system operating smoothly.


A number of distinct structural elements define the nature and character of the U.S. Congress. At the top level, Congress is divided into two chambers of roughly equal legislative authority (symmetrical bicameralism), and the necessity of getting both chambers to agree to the details of legislation tend to produce a slow and contentious political process that often bogs down in gridlock. Within each chamber the important structural elements are 1) the party leadership structure; 2) the committee structure, with each committee have its own subject matter jurisdiction; and 3) the structure of log rolling, in which legislators trade votes to help build support for various items of legislation.