Members of Congress are responsible for both representation and national lawmaking, both of which must take place within the constraints of partisanship. These two duties are often at odds because what is good for a local constituency may not be beneficial for the country as a whole, and partisanship requires that members also consider what is best for their party.  In an era of heightened partisanship, or hyperpartisanship, which can cause increased party polarization, it can become hard to find common ground on which to craft solutions to national problems.

Representation style takes four different forms—policy representation, allocative representation (including the infamous pork barrel spending, also referred to as earmarks), casework, and symbolic representation—and congresspersons attempt to excel at all four. However, since the legislative process designed by the founders is meant to be very slow, representatives have fewer incentives to concentrate on national lawmaking when reelection interests, and therefore local interests, are more pressing.

The founders created our government with a structure of checks and balances centered around our bicameral legislature. Not only do the two houses check each other, but Congress can check the other two branches, including the prerogative of congressional oversight, which allows Congress to keep tabs on the executive, and the House and the Senate may be checked by either the president or the courts. Congress is very powerful but must demonstrate unusual strength and consensus to override presidential vetoes and to amend the Constitution.

Citizens and representatives interact in congressional elections. Seats are allocated among states through the process of reapportionment and the districts are drawn up through redistricting to correct for malapportionment. Gerrymandering and racial gerrymandering make redistricting a highly political process. Congressional races can be influenced, among other things, by the powerful incumbency advantage, the presidential coattail effect, and the phenomenon of the midterm loss.

The majority party in each house has considerable power because it determines leadership positions, including the Speaker of the House, which are filled by the party caucuses. The business of Congress—crafting legislation and engaging in legislative oversight—is done in committees where the leadership is determined by party leaders and by the seniority system. Standing committees, including the powerful House Rules Committee, do most of the work, although select committees, joint committees, and conference committees are key as well.

Laws get placed on the legislative agenda in a variety of ways, often through the efforts of policy entrepreneurship. They go first to committee before being reported onto the floor, where they are discussed, debated, and subject to a roll call vote. In the Senate, the filibuster can prevent a vote unless cloture is obtained. Often, the only way consensus can be found is to bundle things everyone likes and dislikes together in omnibus legislation. When the bill emerges from Congress it goes to the president, who can sign it or veto it (or kill it with the less public pocket veto), subject to a veto override by both houses.