America's Electoral System (3): How Congress Is Elected: Senate, House and Redistricting
[Key points]
Senators: two per state regardless of population, six-year terms, about a third elected every two years. House members: 435 seats apportioned by population, two-year terms, all elected at once
The contrast is the Great Compromise of 1787 between large and small states
House districts are redrawn after every census - and 'gerrymandering' is the art of drawing them for partisan advantage
1. The Senate: two votes per state, six-year terms
The Senate has 100 seats, two for every state, regardless of population - Wyoming, with under 600,000 people, matches California, with nearly 40 million. This equality was the price small states demanded at the Constitutional Convention in 1787, in what became known as the Connecticut Compromise.
Senators serve six-year terms, divided into three classes so that roughly one-third of the chamber stands for election every two years; the Senate is never replaced all at once. Senators are elected statewide - by direct popular vote since the Seventeenth Amendment in 1913 (state legislatures chose them before). A senator must be at least 30, a citizen for nine years, and a resident of the state. Beyond legislation, the Senate alone confirms presidential appointees (cabinet secretaries, federal judges, ambassadors), ratifies treaties by a two-thirds vote, and tries impeachments. The vice president serves as its president and votes only to break ties.
2. The House: seats by population, the whole chamber every two years
The House has 435 seats distributed among the states by population. After each decennial census, the seats are reapportioned - fast-growing states gain, slow-growing states lose. Representatives serve two-year terms and all 435 face the voters every even-numbered year, making the House the chamber most sensitive to shifts in public mood. A representative must be at least 25, a citizen for seven years, and a resident of the state. After the 2020 census, the average district held about 761,000 people. The District of Columbia and the territories elect non-voting delegates or a resident commissioner outside the 435. The House alone may originate tax bills, impeach federal officials, and choose the president when the Electoral College deadlocks (Chapter Two).
3. Who draws the lines - and why it matters
Once a state knows how many seats it has, someone must draw the districts. In most states the legislature draws the map and the governor signs it - an inherently political process. California, Arizona, Michigan and a few others instead use independent or bipartisan citizens' redistricting commissions that bar legislators from the work.
Line-drawing shapes outcomes: 'packing' opponents into a few districts, or 'cracking' them across many, can tilt a state's delegation. The practice has a name - gerrymandering - after an 1812 Massachusetts district, approved under Governor Elbridge Gerry, that resembled a salamander. In Rucho v. Common Cause (2019), the Supreme Court held that partisan gerrymandering presents a political question federal courts cannot police; race-based line-drawing remains constrained by the Constitution and the Voting Rights Act, and districts within a state must be nearly equal in population.
In 2025-26, a rare mid-decade redistricting fight broke out. Texas adopted a new congressional map in 2025. California voters answered on November 4, 2025, approving Proposition 50 with about 64.4 percent: for the 2026, 2028 and 2030 cycles, California will use maps drawn by the state legislature, returning the job to its independent citizens' commission after the 2030 census. Supporters called the measure a necessary counter to Texas; opponents said it bypassed the independent commission voters had created. In February 2026 the Supreme Court declined to block the new California map from being used this year, according to the Associated Press and NPR. The practical consequence for voters: your congressional district in 2026 may not be the one you voted in last time - check your address before you vote.
(Previous: how the president is elected. Next: what the 2026 midterms will decide.)
Related: America's Electoral System (4): The Midterms: What Is on the Ballot on November 3, 2026
Source: GSM · USA (original Chinese edition)
Photo: 图：美国国会众议院议场。众议院435席每两年全部改选。图片来源：美国众议院／Wikimedia Commons（公共领域）
- 2026-10-20America's Electoral System (1): The Big Picture: What U.S. Elections Actually Decide
- 2026-10-20America's Electoral System (2): How the President Is Elected: The Electoral College and the Road to 270
- 2026-10-20America's Electoral System (3): How Congress Is Elected: Senate, House and RedistrictingThis story
- 2026-10-20America's Electoral System (4): The Midterms: What Is on the Ballot on November 3, 2026
- 2026-10-20America's Electoral System (5): Primaries and Nominations: How Candidates Are Chosen
- 2026-10-20America's Electoral System (6): How Voters Cast Ballots: California in 2026 as an Example
- 2026-10-20America's Electoral System (7): Counting, Certification, and a Path into Public Office
