Blog · Politics guide
How the U.S. Congress works and why midterm elections matter
Every two years, the United States elects all of the House and a third of the Senate. To see why those votes matter so much, it helps to know what each chamber does and what a majority can and cannot do.
Two chambers, two logics
The U.S. Congress has two chambers that must agree to pass a law. The House of Representatives has 435 voting members, distributed among the states by population, each serving a two-year term. There are also five delegates (Washington, D.C., the Virgin Islands, Guam, American Samoa and the Northern Mariana Islands) and a resident commissioner for Puerto Rico who take part but do not vote when the House sits as the full House, according to its official site.
The Senate has 100 members: two per state regardless of its size, serving six-year terms. Senators are split into three groups, called classes, so roughly one third is renewed every two years. That is why the whole Senate never changes at once, and why a voter can see a Senate race on the ballot this year and none two years later, as USA.gov explains.
What is on the ballot in a midterm
It is called a “midterm” because it falls halfway through the president’s four-year term. The president is not on the ballot, but all 435 House seats are, along with part of the Senate and many state and local offices. The result decides which party holds the majority in each chamber for the next two years, and that shapes what the president can accomplish.
In the United States the president’s party often loses ground in these elections, but it is not a rule: it depends on the year, the district and how tight the margins are.
How an idea becomes law
- A bill is introduced. A lawmaker files it in either chamber (with one exception: bills that raise revenue must start in the House).
- It goes through a committee. Standing committees have defined areas, such as finance, defense or health; they study the text, amend it and decide whether it moves forward. Each committee has a chair from the majority and a ranking member from the minority.
- It is voted on the floor. With all 435 seats filled, 218 votes make a majority in the House. In the Senate a simple majority is 51; in a 50–50 tie the vice president breaks it, presiding over the chamber but voting only in that case.
- Both texts must match. If the chambers pass different versions, they must be reconciled and voted on again.
- The president signs or vetoes. A veto can only be overridden by two thirds of both chambers.
In the Senate, the rule allowing unlimited debate (the filibuster) means most bills need 60 votes to end discussion and reach a vote. That is why passing laws without cross-party agreement is usually harder there than in the House.
What each chamber can do on its own
- The House originates revenue bills and holds the power to formally impeach senior officials. By custom, spending bills also start there.
- The Senate tries those impeachments: conviction takes two thirds of those present. It also confirms, with its advice and consent, ambassadors, Supreme Court justices and other senior posts the president nominates, and treaties need two thirds of those present.
What changes when the opposition controls a chamber
When the president belongs to one party and at least one chamber is controlled by the other, it is called divided government. That majority can do several concrete things: decide which bills reach the floor, lead the committees, open investigations and oversee government agencies, and block laws the president wants. In return, the president keeps the veto and the ability to govern through executive actions, which can be challenged in court.
The budget is where it shows most. The federal government needs Congress to approve its funding before a deadline; if there is no deal, part of its activities shut down, which is called a shutdown. That makes every funding deadline a negotiating opportunity for the majority in each chamber.
Aster covers these disputes in its politics section. For example, the story on the result of the November 3, 2026 midterm elections and the one following the debate over federal funding, which according to that coverage expires on December 11. Both attribute each claim to its source.
How to follow a vote without getting confused
- “The House passed it” is not “it’s law.” It still needs the Senate, matching texts and the president’s signature.
- Look at the numbers, not just the outcome. A 218–214 passage and a 330–90 one weigh differently, and so does how many members voted against their own party.
- Tell approving a budget apart from spending it. A funding law authorizes spending with rules and deadlines; a political deal can take time to become text.
- Check the official source. On Congress.gov you can see the text of bills, their status and how each lawmaker voted.
The short version
Congress has two chambers with different rhythms: the House is renewed entirely every two years and the Senate by thirds. A midterm does not change the president, but it can change who controls the committees, the agenda, the investigations and the budget. No majority does everything alone: laws need both chambers and the president’s signature, and a veto can only be overridden with two thirds. That is why a midterm can shift a lot without changing who sits in the White House.