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Congress is the legislative branch of the United States federal government, established by Article I of the Constitution — the longest and most detailed Article, a deliberate signal of the Founders' expectation that the legislature, as the branch closest to the people, would be the dominant institution. Congress is bicameral, composed of the House of Representatives and the Senate, two chambers of broadly equal legislative weight but very different character. For Edexcel A-Level Politics Component 3, a secure grasp of Congress's structure, powers and legislative process is essential, and the comparison with the UK Parliament — a bicameral body in which one chamber is overwhelmingly dominant and fused with the executive — is among the most fertile on the course. This lesson examines the two chambers, the full range of congressional powers, the legislative process, the committee system, the impact of partisan polarisation, and the comparison with Westminster.
Congress's bicameral design was itself a product of the Great Compromise, which reconciled large states (who wanted representation by population) with small states (who wanted equal representation) by giving each its preferred principle in a different chamber. The two houses differ in size, term length, basis of representation and political culture.
| Feature | Detail |
|---|---|
| Members | 435 voting members |
| Term | 2 years (every seat is contested at every election) |
| Representation | Apportioned by state population, reallocated after each decennial census |
| Minimum age | 25 years old |
| Presiding officer | Speaker of the House (in practice the leader of the majority party) |
| Exclusive powers | Initiate revenue (tax) bills; impeach federal officials |
The House's two-year term makes it the more electorally sensitive chamber, perpetually attuned to shifts in public mood; representatives are, in effect, always campaigning. Because seats are apportioned by population, large states such as California command a substantial bloc of representatives while the smallest states have only one, so the House broadly reflects the distribution of the population — subject to the distorting effects of district boundaries.
| Feature | Detail |
|---|---|
| Members | 100 (2 per state, regardless of population) |
| Term | 6 years (one-third of seats contested every two years) |
| Representation | Equal — every state has exactly two senators |
| Minimum age | 30 years old |
| Presiding officer | The Vice President (with a tie-breaking vote); day-to-day presiding falls to the President Pro Tempore |
| Exclusive powers | Confirm presidential appointments; ratify treaties (two-thirds majority); try impeachments |
The Senate's six-year terms and the staggering of elections (only a third of the chamber faces the voters at once) were designed to insulate it from transient passions and make it the more deliberative, stable body — what tradition calls the "cooling saucer" into which the hotter brew of the House is poured. The principle of equal state representation has a profound and controversial consequence: because every state has two senators irrespective of population, the smallest states wield the same Senate power as the largest, so a minority of the national population can command a majority of the Senate. This "malapportionment" is a recurring theme in evaluations of US democracy and has no parallel in the elected chamber of any comparable democracy. Defenders reply that equal state representation is the deliberate guarantee of the federal bargain — the price of union, protecting small states from being overwhelmed — and that it is permanently entrenched, since Article V provides that no state may be deprived of its equal Senate suffrage without its consent. Critics counter that a chamber in which a senator representing a few hundred thousand people has the same vote as one representing tens of millions is hard to reconcile with the democratic principle of political equality, an effect magnified because the Senate also controls confirmations and can block legislation through the filibuster. The argument over the Senate is thus an argument about the proper balance between federalism and majority rule — a tension that runs through the whole American system.
Key Point: The Senate is often regarded as the more prestigious and powerful chamber because of its exclusive powers over appointments and treaties, its longer terms, its smaller size (which gives each member greater individual weight), and the filibuster. This contrasts sharply with the UK, where the unelected House of Lords is firmly subordinate to the elected House of Commons. The US thus has two genuinely powerful chambers, whereas the UK has one dominant chamber and a revising one.
Congress's primary function is lawmaking, and its legislative authority is formidable but shared. A bill must pass both chambers in identical form before it can be sent to the President. Congress may legislate on any matter within its constitutional authority — taxation, spending, defence, interstate commerce, immigration and much else — and the broad judicial reading of the commerce and elastic clauses has stretched that authority far beyond the literal enumerated list. The requirement that both co-equal chambers agree, however, builds bicameral friction into every law, and is a major reason why so much proposed legislation fails.
Congress's control of the nation's finances — the power of the purse — is arguably its single most potent weapon and the foundation of its check on the executive. The federal government cannot spend a dollar that Congress has not appropriated. Revenue bills must originate in the House, both chambers must pass the annual appropriations that fund the government, and the President depends on Congress for the money to pursue almost any policy. When Congress and the President cannot agree on funding, the result is a government shutdown, in which non-essential federal operations cease until a deal is struck — a recurring spectacle that demonstrates the purse power in its rawest form and the leverage it gives the legislature.
A closely related lever is the debt ceiling, the statutory limit on federal borrowing that Congress must periodically raise to allow the government to meet obligations it has already incurred. Because failing to raise it would risk a catastrophic default, the debt ceiling has become a high-stakes bargaining chip that a congressional majority can use to extract concessions from the President. Both the shutdown and the debt-ceiling stand-off illustrate a deeper point: the power of the purse is not merely a formal authority but a recurring source of real political leverage that can force an executive to negotiate. The same tools, however, can be used irresponsibly, turning routine fiscal housekeeping into manufactured crises — which is itself a strand of the critique that polarisation has degraded Congress.
Congress monitors and investigates the executive branch — a function known as oversight — through several instruments:
Oversight is how Congress holds the administration accountable between elections, though its vigour depends heavily on whether the same party controls both the legislature and the White House. When the opposition controls a chamber, investigations multiply and become combative; when the President's own party is in charge, scrutiny tends to slacken. This partisanship of oversight is itself a significant weakness, because it means accountability is strongest precisely when it is most politically motivated and weakest when independent scrutiny might matter most — a point candidates can use to qualify any claim that Congress is an effective check on the executive.
The Constitution grants Congress the power to declare war (Article I, Section 8), reflecting the Founders' determination that the decision to commit the nation to war should rest with the people's representatives, not a single executive. In practice, however, presidents have repeatedly committed forces to sustained combat without any formal declaration of war, and Congress has not declared war since 1942. In an attempt to reclaim its authority, Congress passed the War Powers Resolution (1973) over a presidential veto, requiring the President to:
Presidents of both parties have questioned the Resolution's constitutionality and have frequently acted as though it does not bind them, so the war power remains one of the clearest examples of authority draining from Congress towards the presidency.
Impeachment is Congress's ultimate check on the other branches, and the two chambers play distinct roles:
Several presidents have faced impeachment, but the crucial fact for candidates to remember is that no President has ever been convicted and removed by the Senate — the two-thirds threshold has always proved insurmountable, especially in an era of partisan loyalty. Impeachment is therefore a powerful weapon in theory but a blunt one in practice, and its limited efficacy is itself revealing: in an age of party loyalty, securing 67 senators to remove a President of their own party has proved politically impossible, so the gravest constitutional check Congress possesses has become largely symbolic.
The Senate's power of advice and consent gives it a major check on the President's control of personnel and foreign policy. It must confirm presidential appointments to the Cabinet, the federal judiciary (including Supreme Court justices) and senior posts, and it must ratify treaties by a two-thirds majority. These powers are far from formalities. The Senate can refuse even to consider a Supreme Court nominee, can subject a nominee to bruising hearings before confirming on a near party-line vote, and can decline to ratify a treaty a President has negotiated, forcing the executive to rely instead on executive agreements that do not require Senate approval. The contentiousness of modern confirmations is itself evidence of how high the political stakes of these powers have become.
Beyond its institutional powers, Congress exists to represent the American people, and a key analytical question is what "representation" actually means. Political scientists distinguish several models, and individual members move between them.
A member acting as a delegate sees their job as faithfully transmitting the wishes of their constituents, voting as the district would vote even against their own judgement. A member acting as a trustee (in Edmund Burke's classic formulation) believes they were elected to exercise their own informed judgement in the national interest, even when that diverges from constituency opinion. In practice most members blend the two, behaving as delegates on issues that are highly salient to their voters and as trustees on more technical or remote questions. Two further models matter: the partisan model, in which a member votes the party line because party increasingly defines their identity and their electoral fate, and the descriptive (or resemblance) model, which concerns whether Congress mirrors the social composition of the nation in terms of gender, race and background.
These models generate rich evaluation. The two-year House term pushes representatives strongly towards the delegate role, since they must constantly answer to their voters, whereas the six-year Senate term gives senators more latitude to act as trustees. Polarisation, however, has strengthened the partisan model at the expense of both, so that a member's party label now predicts their votes more reliably than either their constituents' interests or their own independent judgement. And on the descriptive measure, Congress has grown markedly more diverse over time but still under-represents women and several minority groups relative to the population — a live point in debates about how democratically representative the institution really is.
Although party discipline is weaker than at Westminster, Congress is not leaderless, and its leadership structures wield significant influence over the legislative agenda. In the House, the Speaker — in practice the leader of the majority party — is the single most powerful figure, controlling the flow of legislation to the floor, influencing committee assignments and acting as the chamber's chief partisan strategist; the Speaker is also second in the line of presidential succession. The Speaker is supported by the majority leader and the party whips, whose job is to count votes and marshal the party's members, while the minority leader heads the opposition party. In the Senate, the majority leader is the pivotal figure, setting the chamber's schedule and deciding which measures reach the floor, though the Senate's traditions and the filibuster give individual senators far more capacity to obstruct than House members enjoy.
The existence of this leadership apparatus is an important corrective to the stereotype of Congress as a chaotic assembly of 535 free agents. Leaders cannot whip their members with the iron certainty of UK party managers — an American legislator who defies the leadership rarely loses their seat as a result — but they can offer or withhold valuable committee posts, campaign support and the scheduling of a member's priorities, giving them real, if softer, leverage. The result is a chamber in which party matters and is organised, yet in which individual members retain a genuine independence unknown in the heavily whipped House of Commons. This intermediate position — stronger party organisation than the stereotype suggests, but weaker discipline than at Westminster — is essential to understanding both why Congress can sometimes act collectively and why it so often cannot, and it should inform any comparison with the tightly disciplined UK Parliament.
The path from bill to law is deliberately long and strewn with obstacles, so that the failure of legislation is the norm and its passage the exception:
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