Midterm prediction market odds favor a Democratic sweep
With voting on Tuesday, Kalshi and Polymarket give Democrats about 93% to 95% odds of taking the House and about 72% for the Senate, with Maine among the closest seats.
Traders have made up their minds ahead of Tuesday. Midterm prediction market odds on both major venues point to Democrats winning the House and, less certainly, the Senate, with a handful of close races deciding how big any majority would be.
What happened
Polymarket's midterms page showed Democrats at 95% to win the House and 72% for the Senate over the weekend, and a 71% chance of a sweep of both chambers in its balance-of-power market, which had about $49 million traded. ThinBlimp's comparison, updated early on Sunday, put Democrats at 93.15 cents on Kalshi and 93.75 cents on Polymarket US for the House, and at 71.5 cents and 71.45 cents for the Senate.
The tightest Senate contests on that table were Kansas, where Democrats traded around 50.5 to 52.5 cents, Iowa, where Republicans were near 55.5 cents, and Maine, where Democrat Troy Jackson was near 68.5 cents against Republican Susan Collins on both venues. Exchange Alpha's volume-weighted blend gave Jackson 68% as of late Saturday.
Prediction Tape noted that Kalshi's House market had traded about 90 million contracts and Polymarket's about $35 million, which makes these some of the deepest political markets ever listed.
Why it matters
Odds are now part of how campaigns, media and investors read the race. CNBC's week-ahead note said investors expect the vote to matter less than the AI trade, but a Democratic Congress could reshape defense, drug pricing and data-center rules. Earlier coverage of Polymarket House odds traced how this consensus built over October.
Depth varies a lot, though. Headline control markets are deep; many district contracts are not, a risk we described in our election odds manipulation report. A 70% price is also far from certain: one in three such favorites should still lose.
Other contests show how lopsided the board looks. ThinBlimp listed Democrats near 69.5 to 70.5 cents in Texas and 70.5 to 71.5 cents in Ohio, and Republicans at about 74.5 cents in Nebraska, where Prediction Tape said Pete Ricketts rose 10 points on Kalshi on Saturday. Movements of that size in the final days are common in thinner state markets. Midterm prediction market odds for the chamber totals have been far steadier, with the House barely moving through the weekend. Governor races add another layer: ThinBlimp showed Florida and Texas favoring Republicans near 64.5 to 67.5 cents and Georgia leaning Democratic near 67.5 to 68.5 cents, prices that would flip quickly on early returns. Turnout and counting speed in each state will decide how fast those contracts settle.
What's next
Polls close from Tuesday evening U.S. time, and slow counts in some states could leave Senate control open for days. Polymarket's midterms dashboard tracks every race.
After results, compare final midterm prediction market odds with outcomes in close seats. That scorecard will shape how much weight markets get in 2028.
The call
We say Democrats win the Maine Senate race. Polymarket's "Will the Democrats win the Maine Senate race in 2026?" market priced Yes at 70% at 08:23 MSK on Nov. 1, with deep liquidity, and Kalshi showed about the same price. Maine's ranked-choice count can take extra days if no one passes 50% in the first round, but both venues have held Jackson near 68% to 69% into the final weekend.
This article is for information only and is not investment advice. Calls are editorial forecasts, logged with market odds at the time of publication and kept on the record.