On November 3, Americans decide which party controls the US Congress for the second half of Donald Trump's presidency.
On November 3, about 210 million registered voters will decide how much power Donald Trump has for the rest of his US presidency.
Trump is not on the ballot, but control of the United States Congress is. Made up of the House of Representatives and the Senate, Congress writes the country’s laws and controls federal spending.
In this visual explainer, Al Jazeera breaks down how the elections work, which races matter and what the results could mean for either party.
What happens in the midterm elections?
Held halfway through a US president’s four-year term, midterm elections decide the makeup of Congress.
All 435 seats in the House of Representatives and 35 of the Senate’s 100 seats are being contested, including special elections in the states of Florida and Ohio to fill the seats vacated by US Secretary of State Marco Rubio and Vice President JD Vance. Voters in 36 states will also elect governors.
House members represent one congressional district each and serve two-year terms, while senators serve six-year terms.
Midterm elections are also widely considered a referendum on the sitting president’s performance.
Since 1946, the president’s party has lost an average of 26.5 seats in the House and a handful in the Senate in midterm elections, according to Todd Belt, a professor of political management at George Washington University.
Beyond Congress and governors, voters will also elect state legislators and local officials.
Nadia Brown, a professor of government at Georgetown University, said that while national elections get most of the attention, “It is important to remember that local politics is where most Americans interact with government.”
She added that “It is the local propositions or referendums on ballots [that] will impact the everyday lives of people.”
What is at stake in the House and Senate?
Republicans hold majorities in both chambers. Losing either would give Democrats the power to block legislation and launch investigations into Trump’s administration.
Democrats need to gain three seats in the House and four in the Senate to take control. A 50-50 split in the Senate would leave Republicans in control, because Vance can cast tie-breaking votes.
Belt said a Democratic victory could significantly limit Trump’s ability to pursue his domestic agenda.
“If Democrats take one chamber, all non-government funding legislation will grind to a halt,” he told Al Jazeera.
How do House elections work?
The House of Representatives is the lower house of the US Congress.
Its 435 members each represent one local district and serve two-year terms, so every seat is contested every two years.
Seats are divided among the states by population, based on the US Census conducted every 10 years. California, the most populous state, has 52 seats, while the least populous, such as Wyoming and Vermont, have one each.
A party needs 218 seats for a majority.
Republicans currently control the House, with 218 seats to the Democrats’ 214, and one independent sits with the Republicans. Two seats are vacant, one last held by each party.
The new House will be sworn in on January 3, 2027.
The House races to watch
Each district elects its own representative, and the party that wins 218 seats takes control, so a few narrow wins in close districts can decide the majority.
Belt estimates that about 35 House races could decide the majority. He predicts Democrats could gain about 15 seats, despite Republican redistricting that he says has given the party an advantage in nine additional districts.
“People generally vote straight ticket, meaning they will vote for all the candidates of one party, so this is likely to affect down-ballot races [as well],” he said.
A battleground district is a seat either party could realistically win. The graphic below highlights 12 of these key races to watch.
How do Senate elections work?
The Senate is the upper house of the US Congress.
Its 100 members, two from each state regardless of population, are elected statewide and serve six-year terms, with about a third of seats contested every two years.
This year, 33 seats are being contested in regular elections, alongside special elections in Florida and Ohio. Those two contests will fill the remaining two years of terms previously held by Marco Rubio and JD Vance.
Of the 35 seats being contested, Republicans hold 22, and Democrats hold 13.
Republicans currently have 53 senators. Democrats have 45, and two independents sit with them, giving the Democratic bloc 47 seats.
Democrats need a net gain of four seats to reach 51 and take control. Republicans can keep control with 50 because Vice President Vance can break tied votes.
The new Senate will be sworn in on January 3, 2027.
The Senate races to watch
To win the Senate, Democrats must hold the 13 seats they are defending and flip Republican-held ones.
In Georgia, Democratic Senator Jon Ossoff faces Republican Mike Collins. Michigan’s open seat pits Democrat Abdul El-Sayed against Republican Mike Rogers, while Democrat Chris Pappas faces Republican John Sununu for an open seat in New Hampshire.