US Congress: Structure and Powers

Congress is bicameral: two chambers, both of which must pass the identical text of a bill before it can become law. The design settled the sharpest argument at the Philadelphia Convention in 1787.

• The Virginia Plan wanted representation by population, which suited the large states.
• The New Jersey Plan wanted every state represented equally, which the small states demanded as the price of joining at all.
• The Connecticut Compromise gave each side one chamber: a House apportioned by population and a Senate with two seats per state.

That bargain is why Wyoming and California each send two senators while their House delegations differ enormously. It also explains a structural feature students often overlook: the two chambers are close to co-equal. Neither can override the other, and there is no equivalent of the Parliament Acts by which the Commons can eventually bypass the Lords.

	House of Representatives	Senate
Represents	Population, by district	States, equally
Members	435 voting members	100
Term	2 years	6 years, in three staggered classes
Elected	Whole chamber together	About a third every two years
Minimum age	25	30
Citizenship	7 years	9 years
Presiding officer	Speaker of the House	Vice-President; in practice the president pro tempore

Article I opens the Constitution and is the longest of the seven articles. The framers expected the legislature, not the presidency, to be the dominant branch.

The House is the chamber of population and of short horizons. Its 435 voting seats were fixed by statute in 1929; before that the chamber grew with the country. Seats are redistributed among the states — apportionment — after each ten-yearly census, with every state guaranteed at least one. Wyoming, the least populous state, has a single representative.

Six delegates from the District of Columbia and the US territories sit in the House, speak and serve on committees, but cannot vote on the floor. They are not counted in the 435.

Structure of power inside the chamber:

• The Speaker is elected by the whole House and is in practice the leader of the majority party. The role combines presiding officer, party leader and floor manager: the Speaker refers bills to committee, appoints members of the Rules Committee, and decides what reaches a vote. The Speaker is also second in the line of presidential succession after the Vice-President.
• Majority and minority leaders run their parties' floor strategy; whips count and secure votes.
• Committee chairs hold the real gatekeeping power, since a bill that a chair declines to schedule usually dies.

The election cycle shapes behaviour. Every representative faces the voters every two years, so a member elected today begins the next campaign almost immediately. That produces a chamber that is highly responsive to district opinion, and one where a narrow majority is fragile.

The 119th Congress (2025–27) began with Republicans holding the House 220–215, and as of September 2026 the margin remains narrow enough that a handful of defections can sink a bill. That hands disproportionate leverage to organised blocs within the majority party. The next congressional elections fall on 3 November 2026; the mechanics of those elections are examined under specification section 5.1.1.

The Senate is the chamber of states, longer horizons and individual power. Each state sends two senators regardless of population. Until the Seventeenth Amendment (1913) they were chosen by state legislatures; since then they have been directly elected.

Six-year terms in three staggered classes mean the Senate is a continuing body — it is not dissolved and re-elected as a whole, so it can act immediately after an election while the House organises itself.

Presiding and leading:

• The Vice-President is President of the Senate but attends rarely, and votes only to break a tie. This is not a ceremonial detail: in July 2025 the tax-cutting bill Trump called his "big, beautiful bill" cleared the Senate only when Vice-President Vance used his casting vote.
• The president pro tempore, conventionally the longest-serving member of the majority party, presides in the Vice-President's absence.
• The Senate Majority Leader schedules floor business but has nothing like the Speaker's control, because Senate rules protect individual members.

Three procedures give individual senators real power:

Procedure	What it does	Consequence
Unanimous consent	Routine business proceeds by agreement rather than formal vote	A single objection stops it, so leaders must bargain
Filibuster	Debate can be extended to prevent a vote	A minority of 41 can block most legislation
Cloture	Ends debate, requiring 60 votes since the threshold was lowered from two-thirds in 1975	The effective threshold for ordinary legislation is 60, not 51

Two routes bypass the 60-vote threshold. The nuclear option — a majority vote reinterpreting the rules — was used by Senate Democrats in 2013 for executive and lower-court nominations, and extended by Republicans in 2017 to Supreme Court nominations; those now pass by simple majority. Reconciliation, created by the Congressional Budget Act 1974, limits debate on qualifying budget measures, which is why so much major economic legislation is routed through it.

As of September 2026 the Senate stands at 53–47 to the Republicans, so on ordinary legislation the majority is well short of 60 and depends on either bipartisan support or reconciliation.

Article I, Section 8 lists what Congress may do. Because these powers are enumerated, the list also implies a boundary: powers not granted lie with the states or the people under the Tenth Amendment.

Power	Text of Article I, Section 8	Modern significance
Taxation and spending	Lay and collect taxes, duties and excises; provide for the general welfare	The foundation of federal grants and of the power of the purse
Borrowing	Borrow money on the credit of the United States	Debt ceiling votes become leverage over the executive
Commerce	Regulate commerce with foreign nations and among the several states	The constitutional hook for most federal domestic legislation
Money	Coin money and regulate its value	Underpins federal control of currency and, by extension, monetary institutions
War	Declare war; raise and support armies; provide and maintain a navy	Formally exclusive to Congress, in practice contested
Post and patents	Establish post offices; secure exclusive rights to inventions and writings	Federal intellectual property and postal law
Courts	Constitute tribunals inferior to the Supreme Court	Congress designs the federal judiciary below the top court
Necessary and proper	Make all laws necessary and proper for carrying the foregoing into execution	The elastic clause, source of implied powers since McCulloch v Maryland (1819)

The war power illustrates how a clear text can drift. Congress last issued a formal declaration of war in June 1942, against Bulgaria, Hungary and Romania. Since 2001 it has instead passed authorisations for the use of military force — the 2001 authorisation after the September attacks and the 2002 Iraq authorisation — which delegate broad discretion to the President. The enumerated power remains congressional; the practice has migrated to the executive.

Some powers belong to one chamber alone. These are examined frequently, and the distinction is easy marks if learnt precisely.

Exclusive to the House	Exclusive to the Senate
Originate revenue bills (Article I, Section 7) — all taxation must begin in the House	Try impeachments — conviction and removal require two-thirds
Impeach — bring charges against federal officers by simple majority	Confirm appointments — Cabinet, ambassadors and federal judges, by simple majority
Elect the President if no candidate wins an Electoral College majority, each state delegation casting one vote (Twelfth Amendment)	Ratify treaties — two-thirds of senators present
	Elect the Vice-President in the same deadlock scenario

Worked example — impeachment split across the two chambers. Impeachment is a two-stage process, and the split is the point of the design. In December 2019 the House impeached President Trump on two articles by simple majority. The Senate then held the trial and acquitted him in February 2020, falling well short of the 67 votes required to convict. The House impeached him again on 13 January 2021 over the attack on the Capitol; the Senate acquitted on 13 February 2021 by 57–43 — a majority for conviction, but ten votes short of two-thirds. Three presidents have been impeached by the House and none has been removed by the Senate, which shows how effectively the two-thirds threshold protects a president whose party holds more than a third of the chamber.

(Extra context — Bill Clinton's impeachment in 1998 and acquittal in 1999, and Andrew Johnson's in 1868, sit outside the specification's post-2000 reference window for presidential examples. Use them as background, not as your core evidence.)

Worked example — the Senate's power over appointments and treaties. In March 2016 President Obama nominated Merrick Garland to the Supreme Court. The Senate majority declined to hold hearings or a vote at all, and the seat was filled in 2017 by Neil Gorsuch under a new president. In December 2012 the Senate voted 61–38 on the UN Convention on the Rights of Persons with Disabilities — a clear majority, yet the treaty failed because ratification demands two-thirds. In March 2021 Neera Tanden withdrew as President Biden's nominee to run the Office of Management and Budget once it was clear the Senate would not confirm her. Note what each case shows: the Senate can block by voting against, by voting insufficiently in favour, or by declining to act.

The powers Congress holds as a whole require agreement between the chambers. Neither can act alone, and the majority thresholds vary.

Concurrent power	Threshold	Note
Pass legislation	Simple majority in both, in identical text	60 votes in practice in the Senate unless reconciliation applies
Override a presidential veto	Two-thirds of both chambers	The only way to legislate against a President's objection
Declare war	Simple majority in both	Unused since 1942; authorisations used instead
Propose a constitutional amendment	Two-thirds of both chambers	Then three-quarters of states must ratify
Confirm a Vice-President under the Twenty-Fifth Amendment	Majority in both	Used in 1973 and 1974
Oversight and investigation	Each chamber acts through its own committees	Covered under specification section 2.2.3
Appropriate funds	Simple majority in both	Failure to agree produces a shutdown

The override as a concurrent power. In December 2020 President Trump vetoed the National Defense Authorization Act, and Congress overrode him — the House on 28 December 2020, the Senate on 1 January 2021 — the only override of his first term. Neither chamber could have done that alone, which is precisely what makes the override concurrent rather than exclusive; why overrides succeed so rarely is examined under specification section 2.2.2.

The appropriations power is the bluntest concurrent instrument. When the chambers and the President cannot agree a funding bill, federal operations without appropriated money stop. The shutdown that began on 1 October 2025 sent hundreds of thousands of federal employees home unpaid while essential services continued, with Republicans and congressional Democrats each blaming the other over health insurance subsidies. It was the fifth funding lapse since 2013; between 1990 and 2013 there were only two shutdowns of significant length, both during Clinton's presidency.

This is a common 30-mark essay, and the marks are in the justification rather than in the verdict. Build the argument from powers, not from prestige.

The case for the Senate:

• It holds powers the House has no share in: confirmation of every senior appointment and every federal judge, and ratification of treaties.
• Six-year terms free senators from continuous campaigning and let them take unpopular positions.
• Statewide constituencies are larger and more diverse than districts, so senators speak for a broader electorate.
• Senate rules empower the individual. One senator can hold up a nomination or force a cloture vote; forty-one can block legislation outright.
• The Senate is smaller and more visible, which makes it the launchpad for presidential candidacies.

The case for the House:

• All revenue legislation must originate there, so the House sets the starting point of every tax debate.
• It alone can impeach, meaning it decides whether the Senate ever holds a trial.
• Majority rule is stronger. A disciplined House majority can move quickly, while the Senate stalls.
• The Speaker's control of the floor and of committee referral is more concentrated than any Senate leader's authority.
• Two-year terms make it more directly accountable, which is a democratic argument rather than a procedural one.

A defensible judgement: the Senate is the more powerful chamber because its exclusive powers reach into both other branches, while the House's exclusive powers are mostly procedural first steps. But on ordinary legislation the chambers are genuinely equal, and in a narrowly divided House — 220–215 as the 119th Congress began — the marginal member of the majority party may matter more than any individual senator.

1. Describing the Senate as an upper house like the House of Lords

The Senate is elected, has exclusive powers the House lacks, and cannot be overridden. Treating it as a revising chamber inverts the relationship and wrecks any comparative answer.

2. Writing that the President is part of Congress

The separation of powers bars overlapping membership. The President cannot introduce a bill, sit in either chamber or vote. Only a member of Congress can introduce legislation.

3. Confusing impeachment with removal

The House impeaches; the Senate tries and may convict. A president who has been impeached has been charged, not removed. Three have been impeached and none removed.

4. Getting the treaty and confirmation thresholds the wrong way round

Treaties need two-thirds of senators present. Appointments need a simple majority, and have done for Supreme Court nominations since the rules changed in 2017. Mixing these up is a precision error that costs AO1 marks.

5. Calling the current position divided government

The 119th Congress, which began in January 2025, has Republican majorities in both chambers alongside a Republican President. That is unified government. Divided government is a real analytical category and applying the label wrongly undermines everything built on it.

6. Treating the filibuster as a constitutional rule

It is a Senate procedural rule, not a provision of Article I. That matters because the Senate can and does change it by majority vote, as it did for nominations in 2013 and 2017.

7. Answering a structure question with a legislative-process narrative

Section 2.1 asks about composition, the election cycle and the distribution of powers. Save the passage of a bill for section 2.2.2, and use the space here on what each chamber is and what it alone can do.