Midterm elections explained: what they are and how they work
Midterm elections give voters a chance to choose their representatives in Congress halfway through a president’s four-year term.
Politics
By Barbara Pazur
The president isn’t elected during the midterms, but control of the House and Senate can change. You’ll also see governors, state lawmakers, and other offices on many ballots.
This article explains what midterms are, how congressional elections work, what changes to expect in 2026, and how prediction markets reflect shifting expectations about the results.
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 are midterm elections?
Midterm elections are congressional elections held halfway through a president’s four-year term. Voters elect members of the House and Senate, but the president and vice president aren’t elected during the midterms.
Congressional elections happen every two years. When they fall halfway between two presidential elections, they’re called midterm elections. The congressional elections held during a presidential-election year are still congressional elections, but they aren’t midterms.
What is the purpose of midterm elections?
Midterms elect the members of Congress who will serve during the second half of a presidential term. The results also determine which party holds a majority in the House and Senate.
That allows voters to keep or change their congressional representation without waiting for the next presidential election. Depending on the state, the same election cycle can also include races for governor, state legislature, and other state or local offices.
Congress has its own constitutional role separate from the executive branch. It makes federal laws, controls federal spending through the legislative process, and carries out oversight of federal agencies and programs. The Senate also considers presidential nominations.
This is why a midterm can change the political environment in Washington even though the person in the White House stays the same.
When are midterm elections held?
Midterm elections take place every four years, halfway between presidential elections. Congressional elections happen more often, every two years, alternating between presidential-election years and midterm-election years.
So the cycle looks like this: you had the 2022 midterms, the 2024 presidential election, the 2026 midterms, and then the 2028 presidential election.
How do midterm elections work?
Before you get to the general election, candidates usually have to make it through their state’s nomination process. In many states that means a primary, though the exact system varies from state to state.
For the House, you vote on the candidates seeking to represent your congressional district. Representatives serve two-year terms, so every voting seat in the House comes up for regular election every two years.
The Senate works differently. Senators serve six-year terms, and the seats are divided into three classes. Roughly one-third normally comes up for election in each federal election cycle, so most senators stay in office while another group of seats goes before voters.
Congressional elections don’t use the Electoral College. That system is used to elect the president and vice president, while House and Senate members are elected through congressional elections.
Midterm elections vs primary elections: what is the difference?
A midterm describes where an election falls within the presidential cycle. A primary is an earlier stage used to determine which candidates move forward under a party or state nomination system.
Election
What it decides
When it happens
2026 example
Primary election
Which candidates advance to the general election under each state’s rules
Dates vary by state
Congressional primaries take place on different dates during the year, with most held before November
Midterm general election
Who wins the offices being contested
Every four years, halfway between presidential elections
House, Senate, and other races are decided in the November 3, 2026 federal general election
They’re not two different versions of the same election:
A midterm describes when the federal general election falls in the presidential cycle.
A primary is an earlier stage used to decide which candidates advance to that general election.
A congressional candidate may compete in a primary first and, if they advance, appear on the general-election ballot.
Primary rules vary by state. Some states use open primaries, others use closed primaries, and some use different variations of those systems.
When are the midterm elections in 2026?
Election Day for the 2026 federal general election is Tuesday, November 3, 2026. That’s the general election date.
Congressional primaries happen earlier in the election cycle, with dates varying by state.
Early voting, absentee voting, registration deadlines, and other voting dates also vary by state, so it’s worth checking your official state election authority for current information.
Which House and Senate seats are up for election in 2026?
Every voting seat in the House is up for election in 2026, while only part of the Senate is. Together, those races determine which party controls each chamber after the midterms.
How many House seats are up for election in 2026?
All 435 voting seats in the US House of Representatives are up for election on November 3, 2026. Representatives serve two-year terms, which is why every House seat comes up for regular election every two years.
You don’t vote directly for which party controls the House. You vote for a representative in your congressional district, and the results across all 435 districts determine which party holds the majority.
When all 435 seats are filled, a party needs at least 218 seats to hold a majority.
Some incumbents are running for another term in 2026, while other districts have open seats because the current representative is retiring or running for another office.
How many Senate seats are up for election in 2026?
There are 35 US Senate elections on November 3, 2026. Thirty-three are regularly scheduled Class II elections, plus two additional Senate elections in Florida and Ohio.
Senators serve six-year terms, but the 100 seats aren’t elected all at once. Senate seats are divided into three classes, with roughly one-third normally coming up for election every two years. The Class II terms being contested in 2026 expire on January 3, 2027.
The regular Class II seats are in Alabama, Alaska, Arkansas, Colorado, Delaware, Georgia, Idaho, Illinois, Iowa, Kansas, Kentucky, Louisiana, Maine, Massachusetts, Michigan, Minnesota, Mississippi, Montana, Nebraska, New Hampshire, New Jersey, New Mexico, North Carolina, Oklahoma, Oregon, Rhode Island, South Carolina, South Dakota, Tennessee, Texas, Virginia, West Virginia, and Wyoming.
Florida and Ohio sit outside that regular Class II schedule. Both have Senate elections in 2026 because vacancies were filled temporarily and voters now elect someone to serve the remainder of those terms.
Who is up for election in the 2026 Senate races?
A Senate seat being up for election doesn’t necessarily mean the senator currently holding it is running again. Some incumbents are seeking another term, while others are retiring, running for another office, or otherwise not seeking reelection.
As of August 2026, 11 senators had announced they would not seek reelection to their current seats. Nine of those seats are in Illinois, Michigan, Minnesota, New Hampshire, Iowa, Montana, Kentucky, North Carolina, and Wyoming.
The lineup can still change before Election Day, so this is only a snapshot of the 2026 Senate races as of August 2026.
Why do House and Senate seat totals matter in the midterms?
Control of a chamber can change when only a relatively small number of seats change hands. That can alter which party sets the agenda in the House or Senate and how much support legislation needs to move through Congress.
The two chambers also have different responsibilities. Both participate in federal legislation and the budget process, while the Senate separately considers presidential nominations and treaties. Congress also conducts oversight of the executive branch.
That gives midterm prediction markets more than one type of outcome to follow. A market might ask who wins one congressional race, which party controls the House or Senate, or how many seats a party holds once the election is resolved.
Do midterm elections affect the president?
Midterm elections don’t re-elect or remove the president, but they can change the political environment the president works in during the remaining two years of the term.
If the president’s party loses control of the House, Senate, or both, the political landscape in Congress changes. Passing legislation may require more negotiation with the opposing party, congressional oversight priorities can shift, and a change in Senate control can affect the confirmation process for presidential nominees.
Midterms are often treated in political coverage as a test of the sitting administration, but voters aren’t casting one national vote on the president. They’re choosing candidates in individual House, Senate, state, and local races.
The results can also point in different directions. A party may gain seats in one chamber while losing them in the other, so there isn’t always one simple national message to take from a midterm election.
How do 2026 midterm prediction markets work?
Prediction markets give you another way to follow changing expectations around the midterms.
Political markets can offer event contracts on clearly defined outcomes, like which party will control the House or Senate, how many seats a party will hold, or who will win a particular race.
The contract price shows how the market is pricing that outcome. If a contract trades at 60¢, you can read that as roughly a 60% market-implied probability, subject to the contract rules and current market conditions.
That probability can move as new information comes in. Polling, primary results, candidate developments, economic data, and other election news can all change how traders assess the outcome.
A market-implied probability isn’t a guaranteed prediction. A contract trading at 60¢ can later move higher or lower, and the final election result may still go the other way.
OG.com currently has midterm prediction markets covering congressional control, Senate seat totals, and individual races.
How to get started with politics prediction markets on OG
With OG.com, you can trade event contracts on real-world outcomes across different market categories.
Create an account:Open an account and complete sign-up, including identity verification. You can use our web or mobile platforms.
Midterms don’t re-elect or remove the president, but they can change control of Congress. That can change the legislative and oversight environment for the remaining two years of the presidential term.
When are midterm elections?
Midterm elections occur halfway through a president’s four-year term. Congressional elections happen every two years, with midterms alternating with presidential-election years.
What are midterm elections?
Midterm elections are congressional elections held halfway through a president’s term. Every House seat and roughly one-third of Senate seats normally face election during a midterm cycle.
When are midterm elections in 2026?
The 2026 midterm general election is on Tuesday, November 3, 2026. Congressional primaries happen earlier in the election cycle, with dates varying by state.
Can a president cancel midterm elections?
No president has unilateral authority to cancel congressional elections. The Constitution gives states and Congress authority over the time, place, and manner of House and Senate elections, and federal law establishes the regular congressional election cycle.
How often are midterm elections?
Midterm elections happen every four years, halfway between presidential elections. Congressional elections happen more often, every two years.
Who can vote in midterm elections?
Voting eligibility is governed by federal and state law and can depend on the election and jurisdiction. For current eligibility requirements, it’s worth checking your state's official election authority.
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