Prediction Markets Price a Democratic Sweep: Kalshi Puts the Senate at a Record 74 Percent
On the eve of the midterms, the traders have made their call: Kalshi priced Democrats' chances of taking the Senate at a record 74 percent on Monday, both big platforms put the House at 94 to 95 percent, and a sweep of both chambers at about 71 to 72 percent.
The last forecast of the midterm cycle does not come from a pollster. It comes from a market. Prediction markets are pricing a Democratic takeover of Congress on the eve of Tuesday's elections: on Monday, Kalshi put Democrats' chances of winning control of the Senate at a record 74 percent, and Kalshi and Polymarket both put the party's chances of winning the House at roughly 94 to 95 percent, with the probability of a Democratic sweep of both chambers around 71 to 72 percent. The prices moved with the final polling — the New York Times/Siena surveys released Sunday showed Democratic candidates leading in all seven Senate battlegrounds polled, by margins from 11 points in Michigan and seven in Texas down to two in Alaska and one in Iowa, although Siena cautioned that most of the races remained within the polls' margins of error.
The individual races show how fast the money has moved. In Kansas, Democrat Adam Hamilton's probability of defeating Republican Senator Roger Marshall climbed to a record 63 percent on Kalshi, up 23 percentage points in a week. In Texas, James Talarico's odds of beating Ken Paxton reached 75 percent, up 34 points since the Republican primary runoff. Michigan showed the markets' reflexes in real time: Abdul El-Sayed's price dipped after Representative Haley Stevens — the Democrat he beat in the primary — endorsed Republican Mike Rogers on Sunday, his PredictIt contract briefly falling to 66 cents, before recovering to 79 percent on Kalshi by Monday morning, his highest level since the August primary. The volume behind the prices is substantial: Kalshi reported $189.6 million in cumulative Senate general-election trading, with Texas ($69.1 million) and Michigan ($22.3 million) accounting for nearly half of it.
Both methods go into Tuesday carrying questions about themselves. The Times' chief political analyst, Nate Cohn, warned Sunday that registered white Democrats were about 30 percent more likely than registered white Republicans to take part in the final battleground surveys, raising the possibility of polling error — while noting the Times/Siena polls performed well in the 2018 and 2022 midterms despite similar gaps. The markets have their own record to defend: Kalshi's chief executive, Tarek Mansour, conceded on X last week that the industry had oversold its 2024 performance. 'We got too excited two years ago,' he wrote on October 26. 'We have learned and have been more precise since.' Researchers cited by Reuters in September found a single trade of under $1,000 could shift implied probabilities by 10 points in most congressional markets they examined — a finding both platforms dispute.
On Tuesday night the markets get their own spotlight, including in this city: Kalshi is hosting election-night watch parties in five cities, New York City among them, and CBS News — which named Kalshi its official prediction-market sponsor in September — plans to work its data into election-night coverage, while CNN and Fox News will not feature market odds in theirs. For New Yorkers, the numbers to watch before a single vote is counted are already on the board: 74 percent for the Senate, better than nine in ten for the House. They are prices, not predictions carved in stone — and after Tuesday, either the markets or the pollsters, or both, will have some explaining to do.
