What is the US Senate? How it works and how senators are elected
The US Senate has 100 members, with two senators representing each state regardless of population.
Politics
By Barbara Pazur
Senators serve six-year terms, but voters don’t elect the whole chamber at once. Roughly one-third of Senate seats face regular election every two years, which is why a single election cycle can change the balance of power without replacing all 100 senators.
This article is for informational purposes only and should not be construed as financial or investment advice. Past performance does not guarantee future results.
What is the US Senate?
The US Senate is one of the two chambers of Congress. The House of Representatives is the other, and together they form the federal legislative branch.
Every state gets two senators regardless of population, giving the Senate 100 seats. Senators represent their entire state. Congress includes both the Senate and the House, so ‘Senate’ and ‘Congress’ don’t mean the same thing.
You may also hear the Senate called the ‘upper chamber.’ That describes its place in the two-chamber structure, but it doesn’t mean it’s superior constitutionally. The House and Senate have different constitutional responsibilities.
What is the purpose of the Senate and why is it important?
The House represents the population through congressional districts. The Senate gives every state equal representation.
Senators also serve longer, staggered terms. Roughly two-thirds of the chamber normally stays in office after each regular federal election, giving the Senate more continuity as its membership changes.
Most bills have to pass both the House and Senate before they can become law. The Senate also has duties the House doesn’t, like voting on presidential nominees, approving treaties, and holding impeachment trials.
Because the Senate votes on legislation, nominations, and other major federal decisions, changing which party holds the majority can change what has enough support to move forward.
How many senators are there?
There are 100 US senators, two from each of the 50 states. Each senator represents the whole state rather than a single congressional district. Senators serve six-year terms, with no federal term limits.
To serve, a senator must be at least 30 years old, have been a US citizen for at least nine years, and live in the state they represent when elected.
What does the Senate do?
The Senate shares lawmaking with the House and also has several responsibilities of its own:
Make federal laws: Work with the House to consider, amend, and pass legislation.
Vote on nominations: Consider presidential nominees, including federal judges and senior executive appointments.
Consider treaties: Give or withhold consent. Approval generally requires two-thirds of senators present.
Conduct impeachment trials: The House decides whether to impeach an official, while the Senate holds the trial.
Oversee government: Committees hold hearings, investigate issues, and review federal activity.
Lawmaking is shared with the House. Confirming presidential nominees, consenting to treaties, and conducting impeachment trials are responsibilities specifically assigned to the Senate.
How does the Senate work?
Much of the Senate’s detailed work happens in committees before an issue reaches the full chamber. Committees review legislation, hold hearings, oversee federal agencies, and consider presidential nominees.
Senators also organize into party conferences. Majority and minority leaders help manage business on the Senate floor, while the vice president serves as president of the Senate and can cast a vote when the chamber is evenly split.
You’ll often hear that the Senate needs ‘60 votes’ to get something done. Most measures themselves require a simple majority, but ending debate on most legislation through cloture generally takes three-fifths of senators duly chosen and sworn, normally 60 when all 100 seats are filled.
Another term you’ll hear a lot is ‘filibuster.’ If you’re wondering what a filibuster in the Senate is, it’s an effort to delay or block action by prolonging debate or using Senate procedure. Cloture is the process senators can use to end that debate and move toward a vote.
How are senators elected?
Voters elect senators statewide. The Seventeenth Amendment, ratified in 1913, established direct popular election. Before then, state legislatures selected senators.
Candidates usually reach the general election through a state primary or another nomination process. A primary generally determines which candidates advance under a party or state system, while the general election determines who wins the Senate seat. Primary rules and dates vary by state.
If a senator leaves office early, the Seventeenth Amendment allows states to provide for temporary appointments and special elections. The exact process depends on state law.
When are US Senate elections?
Senate elections happen every two years, even though senators serve six-year terms. That includes both presidential-election years and midterm-election years.
You can think of the 100 seats as split into three groups called Classes I, II, and III. Roughly one-third of the Senate comes up for regular election in each federal election cycle, so most senators remain in office while one group of seats goes before voters. That staggered system is why the Senate is considered a continuing body.
If Class I faces election in one cycle, Class II follows two years later, and Class III two years after that. Two years later, six years after the first election, Class I comes up again. Then the cycle continues.
House vs Senate: what is the difference?
The House and Senate both make federal law, but their structure and constitutional responsibilities differ.
Feature
Senate
House of Representatives
Representation
Two senators per state
Seats distributed by state population
Members
100
435 voting representatives
Regular term
Six years; roughly one-third elected every two years
Two years; all seats elected every two years
Distinct powers
Confirmations, treaty consent, impeachment trials
Revenue bills originate here; the House can impeach
Both chambers normally have to approve the same version of a bill before it can go to the president. If the House and Senate pass different versions, those differences have to be resolved before the bill can move forward.
What to know about the 2026 Senate elections
The 2026 federal general election is on November 3, 2026. Senate primaries happen earlier, with dates set by each state.
In 2026, the 33 regularly scheduled Class II seats have terms ending January 3, 2027. Florida and Ohio also have elections to fill unexpired Senate terms, bringing the total number of Senate races to 35.
Those results determine the chamber’s party balance. Because the Senate votes on bills, nominations, and other federal business, a change in that balance can change which proposals or nominees have enough support to advance.
With 100 seats, 51 senators make up a numerical majority. If the chamber is split 50–50, the vice president can cast a tie-breaking vote when senators divide evenly.
For current candidate lists and state-specific election dates, check the relevant state election office or the Federal Election Commission.
How do Senate election prediction markets work?
Senate election prediction markets turn defined election outcomes into event contracts. A market might ask which party will control the Senate, whether a party reaches a stated seat total, or who wins an individual Senate race.
A contract trading around 60¢ can be read as roughly a 60% market-implied probability of the stated outcome under the contract rules.
Senate election market prices can move when new polling or primary results come in, when there are developments involving a candidate, or when campaign news changes the race. Broader economic or political developments can also affect prices, as can changing views of which Senate seats are competitive.
A 60% market-implied probability means the market is pricing roughly a 60% chance of that outcome at that point in time. That probability can change as new information comes in, and it doesn’t guarantee the election result.
Settlement ultimately depends on the outcome defined in the contract rules.
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Create an account:Open an account and complete sign-up, including identity verification. You can use our web or mobile platforms.
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Voters elect senators statewide, meaning each senator represents the entire state rather than a single congressional district. Senators serve six-year terms.
What is a filibuster in the Senate?
A filibuster is an effort to delay or block Senate action through extended debate or other procedural tactics.
How many votes are needed to pass a bill in the Senate?
Most bills can pass with a simple majority. If all 100 senators vote, that normally means 51 votes. If the vote is tied 50–50, the vice president can cast the tie-breaking vote.
The Constitution also requires higher thresholds for certain actions, like overriding a presidential veto or convicting an impeached official.
How many senators does each state have?
Every state has two senators, regardless of population.
How often are senators elected?
Regular Senate elections happen every two years, with roughly one-third of seats up each cycle.
How many Senate seats are up for election in 2026?
There are 33 regular Class II elections plus vacancy-filling elections in Florida and Ohio, for 35 Senate races.
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