US Midterms Explained: A Guide to Betting on US Politics
Halfway through every presidential term, American voters get the chance to change who controls Washington. With Donald Trump's Republicans defending both chambers of Congress, the midterm odds have become one of the busiest political markets of the year. Here is what is being decided, where things stand a month out and how the betting works.
What are the midterms?
The midterms are the federal elections held two years into a four-year presidential term. The president is not on the ballot, but Congress is. The House of Representatives and the Senate pass laws and set budgets, and the Senate also confirms judges and cabinet picks. A president who loses Congress loses much of the power to govern.
The 2026 midterms take place on Tuesday 3 November.
What is on the ballot
All 435 seats in the House are contested, because every member serves a two-year term. In the Senate, 35 of the 100 seats are up. That is 33 regular seats plus special elections in Ohio and Florida, which fill the seats JD Vance and Marco Rubio left when they joined the Trump administration.
Voters in 36 states also elect a governor.
Where the balance of power stands
Republicans hold 53 Senate seats to the Democrats' 47, a total that includes two independents who vote with the Democrats. Democrats need a net gain of four seats to reach 51, since Vice President Vance breaks any 50-50 tie.
The House is tighter. A party needs 218 seats for a majority, and Democrats are four short. Mid-decade redistricting has also shifted the map. Texas drew five new Republican-leaning districts, and California voters answered by passing Proposition 50, which redrew five Republican-held seats in the Democrats' favour.
Why history points one way
The president's party almost always loses ground in midterms. In the past century it has gained House seats only three times, in 1934, 1998 and 2002. The last time Trump was in the White House, Democrats gained 41 House seats in 2018 and took control.
The polls agree so far. The generic ballot asks voters which party they would back for Congress, and Nate Silver's average on 30 September had Democrats 9.6 points ahead among likely voters.
The Senate races to watch
The Senate is harder for Democrats, as a majority means winning in states Trump carried in 2024. Silver's averages have Democratic candidates narrowly ahead in Texas, Maine, Ohio, Iowa, Michigan and Alaska, with leads of between 1.7 and five points.
Texas is the standout. Senator John Cornyn lost the Republican nomination to Ken Paxton, and Democrat James Talarico leads by 3.4 points. In Maine, Susan Collins is the only Republican defending a seat in a state Kamala Harris won. Democrats must also hold Georgia, where Jon Ossoff is running again, and the open seat in Michigan.
How to bet on the midterms
The headline markets are which party wins the House and which wins the Senate. Markets can also cover a combined outcome, such as Democrats taking the House while Republicans keep the Senate. Below that sit individual Senate and governor races, which make up much of the political betting calendar in a midterm year.
Treat the polls with some caution. A review by the American Association for Public Opinion Research found national polls at the 2020 election had their largest error in 40 years, underestimating Republican support. A three-point lead in a Senate race is well within that range.
Results can also take time. Close races in states that count postal votes slowly can stay open for days after polls close, and Georgia goes to a runoff if no Senate candidate wins more than 50% of the vote.