Polymarket and Kalshi midterm odds: who will control the Senate and the House in 2026?
Markets give Democrats about a 67% chance of winning the Senate and about 92% for the House, with a Democratic sweep the single most likely outcome. The balance-of-power odds, the Senate seats that decide it, and how the markets compare with forecast models.
Prediction markets expect Democrats to win both chambers of Congress on 3 November 2026. Polymarket gives Democrats about a 66.5% chance of winning the Senate and 92.5% for the House; Kalshi has 67% and 91%. A Democratic sweep is the single most likely outcome, at about two in three.
Prices as of 22 October 2026. Odds move daily; see the live markets below.
Midterm odds at a glance
| Market | Polymarket | Kalshi |
|---|---|---|
| Senate: Democrats win | 66.5% | 67% |
| Senate: Republicans win | 33.5% | 34% |
| House: Democrats win | 92.5% | 91% |
| House: Republicans win | 7.5% | 9% |
Polymarket's Senate market has traded about $7.7 million and its House market about $19.9 million. Live prices: Senate on Polymarket · House on Polymarket · Senate on Kalshi · House on Kalshi.
Balance of power
Polymarket's combined market, the largest midterm market on the site at about $29.6 million traded, prices the four outcomes:
| Outcome | Chance |
|---|---|
| Democrats sweep | 66.5% |
| Republican Senate, Democratic House | 24.5% |
| Republicans sweep | 7.5% |
| Democratic Senate, Republican House | 0.9% |
See the balance of power market. The House is close to settled in traders' minds; almost all the uncertainty is about the Senate.
The Senate math
Republicans hold the Senate 53–47. Because Vice President JD Vance breaks ties, Democrats need 51 seats, a net gain of four. Here are the races that decide it, with Polymarket prices:
| State | Held by | Favourite | Chance |
|---|---|---|---|
| North Carolina | R (open) | Roy Cooper (D) | 96.5% |
| Alaska | R | Mary Peltola (D) | 74.5% |
| Ohio (special) | R | Sherrod Brown (D) | 70.5% |
| Texas | R | James Talarico (D) | 67.5% |
| Maine | R | Troy Jackson (D) | 65.5% |
| Iowa | R (open) | Ashley Hinson (R) | 56.5% |
| Kansas | R | Roger Marshall (R) | 61.5% |
| Nebraska | R | Pete Ricketts (R), against independent Dan Osborn | 70.5% |
| Michigan | D (open) | Abdul El-Sayed (D) | 69.5% |
| Minnesota | D (open) | Peggy Flanagan (D) | 86.5% |
| New Hampshire | D (open) | Chris Pappas (D) | 90.5% |
| Georgia | D | Jon Ossoff (D) | 96% |
If every favourite won, Democrats would flip five Republican seats and hold all of their own, for 52 seats. But the five pickups are not independent: if polls are off in Republicans' favour, they are likely to be off in several states at once, which is why the market prices Senate control well below what the individual races might suggest. Race-by-race pieces: Texas · Maine · Ohio · Iowa.
Markets vs models
Forecast models are less bullish on the Senate. Decision Desk HQ gave Democrats about a 56% chance in October, against the markets' 67%. On the House the two broadly agree. The Senate number has also moved quickly: Kalshi had Democrats at about 62% on 15 October, and most of the move since came from Maine.
Who has been right more often? Markets and models both have good and bad years; our look at how accurate prediction markets are and the Brier score explains how to judge them.
How these markets resolve
Senate and House control markets resolve on which party holds a majority when the new Congress is seated, under each market's rules, not on election-night calls. Independents who caucus with a party are usually counted with it; read the rules for edge cases (how markets resolve). Some races, such as Maine's ranked-choice count or a Georgia runoff, can take days or weeks.
Midterm odds: frequently asked questions
Who is favoured to win the Senate in 2026?
Democrats, at about 67% on Polymarket and Kalshi as of 22 October 2026.
Who is favoured to win the House?
Democrats, at about 91–92.5%.
How many seats do Democrats need to win the Senate?
A net gain of four, for 51 seats; at 50–50 the vice president breaks ties for Republicans.
What is the most likely balance of power?
A Democratic sweep, at about 66.5% on Polymarket.
When is the election?
Tuesday, 3 November 2026.
