Election Day is near and prediction markets are leaning hard toward one outcome: Kalshi and Polymarket traders expect Democrats to flip the Senate, not just hold the House. If that holds, the effects of a blue wave would reach the entire country, with Republicans trying to avoid losing both chambers.
The gap between forecasters and the markets has narrowed, too, with professional modelers largely landing in the same range as the contract prices. That’s what the markets are signaling hours before the final votes are cast.
Senate control odds today: markets and forecasters side by side
On Kalshi, Democrats’ odds to take the Senate sit at 69%, with the House priced at a much steadier 91%. Polymarket’s own Senate-control market shows Democrats closer to 73%, a gap that reflects how differently the two platforms’ traders are pricing the same uncertain races.
Independent forecaster Nate Silver puts the numbers even higher: a 95% chance for the House and odds in the high 70s for the Senate, figures he’s acknowledged run above where the markets sit. The nonpartisan Cook Political Report frames it differently, counting seven Senate races still within the margin of error heading into Tuesday: close enough, in other words, that the final math could shift in either direction before votes are counted.
The six races Democrats need: North Carolina, Ohio, Maine, Alaska, Texas, Kansas
Democrats need a net gain of four seats to take the chamber, and Polymarket traders currently favor them in six races that would get them there.
North Carolina looks like the safest of the group, with Roy Cooper trading near 98% against Michael Whatley on Polymarket. Ohio (Sherrod Brown over Jon Husted), Maine (Troy Jackson over Susan Collins) and Alaska (Mary Peltola over Dan Sullivan) all sit in the low-to-mid 70s. Texas is the marquee race of the cycle: James Talarico has climbed to 76% against Ken Paxton, a striking number in a state that hasn’t elected a Democrat statewide since 1994. Kansas is tighter: Adam Hamilton’s lead over Roger Marshall has widened into the low 60s, in a state that hasn’t sent a Democrat to the Senate since 1932.
Before getting into the numbers below, it’s worth checking our Polymarket review, the current Polymarket promo code, and download the Action Network app for more picks and analysis heading into Election Night.
Democrats only need to hold 4 of these 6 to flip the chamber. Here’s where Polymarket has each one as of today:
| State | Democrat | Republican |
| North Carolina | Roy Cooper — 98% | Michael Whatley — 2% |
| Texas | James Talarico — 76% | Ken Paxton — 25% |
| Maine | Troy Jackson — 75% | Susan Collins — 26% |
| Alaska | Mary Peltola — 74% | Dan Sullivan — 27% |
| Ohio | Sherrod Brown — 73% | Jon Husted — 28% |
| Kansas | Adam Hamilton — 62% | Roger Marshall — 39% |
Where Republicans are favored: Iowa and South Carolina
Not every red state is trending blue. Polymarket traders still favor Republican Rep. Ashley Hinson over Democrat Josh Turek in Iowa, despite polling that’s hinted at a tighter race than the market price suggests.
In South Carolina, GOP Sen. Darline Graham is a heavy favorite against Democrat Annie Andrews, priced at 69% to win. Those two races are a reminder that the picture isn’t uniformly blue, Republicans are still expected to hold their ground in traditionally safe territory.
What would have to go wrong for the market to miss
Prediction markets have a mixed track record, and the people who study them closely don’t all agree on how much weight their prices deserve.
Thomas Miller, who directs Northwestern’s data science master’s program, runs Kalshi and Polymarket prices through his own statistical model and gets a different answer than the raw contract prices show: on Oct. 27, his model put Republicans’ odds of holding the Senate at 23.4%, well below the roughly 36% Kalshi was pricing that same day. “Prediction market trades provide event contract prices, not probabilities,” Miller has said of that gap.
A few data points back up that skepticism:
- A University of Iowa study comparing 44 election contracts against Kalshi found that outcomes trading around a 20% probability resolved YES in under 1.5% of cases — a gap the researchers tied to momentum pushing prices around rather than real changes in what was likely to happen.
- Kalshi had Flávio Bolsonaro near 80% to win Brazil’s presidency right before he lost.
- In Wisconsin’s Democratic primary for governor this past August, Francesca Hong was priced above 95% and still lost by a fraction of a point.
If you want to read more about politics and elections, visit Prediction Proand read our midterms predictions.
Final-day checklist: fees, liquidity and how the market resolves
Both prediction market platforms work the same basic way: a contract trades somewhere between 1 and 99 cents, with the price standing in for the implied probability, and it pays out $1 per share if the outcome hits or nothing if it doesn’t.
Kalshi charges a small per-contract trading fee and is regulated by the CFTC; it has taken in more than $114 million in trading on its standalone Senate-control contract, and traders have put $73.3 million into its separate “balance of power” market covering both chambers together.
Polymarket has historically charged no trading fee, though that’s begun to change on some market categories this year, and its national Senate contract alone shows north of $16 million traded. Both platforms settle contracts against official results once a race is called, so the final odds won’t move again until the votes are actually counted. With early counts expected the moment polls close in the East, Tuesday night should settle most of this list well before sunrise.
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