US midterm elections 2026: Prediction markets bet on Democrats winning Senate; Republicans face tough battleground fight

Prediction markets are increasingly favouring Democrats to take control of both chambers of the US Congress in Tuesday's midterm elections, with traders on Kalshi giving the party a 74% chance of winning the Senate and a 94% probability of securing the House as of noon ET on Monday.

The odds suggest a strong shift in favour of Democrats as voters prepare to decide the closely watched midterm races. Kalshi's latest assessment marks an increase of around 11 percentage points in the party's Senate-winning probability from approximately 63% on October 2.

On Polymarket, another major prediction platform, traders assigned Democrats a 73% probability of winning the Senate, according to Benzinga.

Quick answers to key questions

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QUESTIONS

As of noon ET on Monday, Kalshi gave Democrats a 74% chance of winning the Senate and a 94% chance of winning the House. Polymarket put their Senate odds at 73%.

Democrats need a net gain of four Senate seats to take control. In the House, they need a net gain of three seats to reach the 218-seat majority threshold.

Prediction market odds reflect trading activity and the prices participants are willing to pay for contracts on election outcomes. They do not measure voter support and are not a substitute for polling.

Polling cited in the article showed Democrats leading in Kansas, Maine, Ohio, Texas and narrowly in Alaska, while they were effectively tied with Republicans in Iowa. These contests could affect the Senate balance.

There is no single nationwide result time; results will emerge state by state as officials count ballots. You can follow updates through official state election websites and major news organisations such as AP, Reuters and The New York Times.

The prediction markets also indicated little expectation of a Republican victory in the House, with Kalshi traders putting the party's chances at just 6%, compared with 94% for Democrats.

While the overall odds have changed little since Sunday, market predictions are increasingly consolidating in favour of Democratic candidates in several competitive Senate races.

Democrats gain ground in key Senate battlegrounds

The latest prediction market trends come as Democratic candidates appear to be making gains in several crucial Senate contests.

The New York Times reported on November 1 that its latest polling with Siena University showed Democrats leading in several battleground states, potentially strengthening the party's prospects of securing a Senate majority.

According to the news outlet, Democrats are ahead in five of the seven states that could determine control of the Senate. These include Kansas, Maine, Ohio and Texas, along with a narrow lead in Alaska. The party is effectively tied with Republicans in Iowa.

The polls are particularly significant because Democratic candidates are leading in five states currently represented by Republican senators and are effectively tied in a sixth.

Kalshi's latest prices for some of the closely watched Senate contests also reflect the momentum.

As of noon ET on Monday, Democratic candidates had the following implied chances of winning:

- Michigan: Abdul El-Sayed had a 78% chance of defeating Mike Rogers in an open seat currently held by Democrats.

- Maine: Troy Jackson had a 73% chance of defeating Republican Senator Susan Collins.

- Ohio: Sherrod Brown had a 71% chance of defeating Republican Senator Jon Husted.

- Kansas: Adam Hamilton had a 63% chance of defeating Republican Senator Roger Marshall.

- Iowa: Josh Turek had a 52% chance of defeating Republican Representative Ashley Hinson.

How many seats do Democrats need to win Senate control?

Republicans currently hold 53 seats in the Senate, while Democrats have 47, including two independents who caucus with them.

With 35 Senate seats up for election, Democrats need a net gain of four seats to secure control of the chamber.

The party must defend all the seats it currently holds while flipping at least four Republican-held seats. A net gain of three would result in a 50-50 Senate, allowing Vice President JD Vance to cast tie-breaking votes and preserve Republican control.

The challenge for Democrats has been particularly significant because several of the seats they need to flip are in traditionally Republican-leaning states.

However, the latest polling and prediction market trends suggest that the party could have a stronger opportunity than previously anticipated.

Democrats have a stronger lead in the House prediction markets

The outlook appears even more favourable for Democrats in the House of Representatives.

All 435 House seats are up for election during the midterms, and a party needs 218 seats to secure a majority.

Republicans currently have a narrow majority following the 2024 elections, when they won 220 seats against Democrats' 215.

Democrats therefore need a net gain of just three seats to take control of the chamber.

However, the latest membership records maintained by the House Clerk list 218 Republicans, 214 Democrats, one independent and two vacancies.

Unlike the Senate, where a handful of statewide contests could determine control, the House outcome will depend on results across dozens of competitive congressional districts nationwide.

Kalshi's 94% probability for a Democratic House victory indicates that traders are strongly anticipating a change in the chamber's political control.

Prediction markets are not the same as political polls

Despite the growing attention surrounding election-related prediction markets, their odds should not be interpreted as conventional polling results.

Platforms such as Kalshi and Polymarket operate differently from traditional political surveys. Their prices reflect trading activity and the willingness of participants to buy and sell contracts based on anticipated election outcomes.

Consequently, prediction market probabilities are not substitutes for polling data and do not necessarily represent the actual share of voters supporting a candidate or political party.

Nevertheless, the platforms have gained considerable traction over the past year, partly driven by the popularity of sports betting and growing interest in event-based trading.

Election-related contracts have also attracted substantial activity. A Bloomberg analysis of data from analytics platform Dune estimated that trading volume across Kalshi and Polymarket had reached around $1.5 billion.

With voting scheduled for Tuesday, traders are increasingly positioning for a Democratic victory in both chambers, although the final outcome will depend on votes counted across the country.