Kalshi Traders Put $1.4 Billion on a Democratic Midterm Sweep

Kalshi's midterm trading volume has surpassed $1.4 billion as of Tuesday, according to data supplied to Fortune, with traders giving Democrats a 93% chance of winning control of the House and a 73% chance of taking the Senate.

The money keeps piling in. A single contract on whether Republicans or Democrats will control Congress has drawn $251 million in trading volume. A similar market on which party controls the House has crossed $181 million. A separate market tracking all four possible combinations of House and Senate control has topped $112 million.

Election Day has pushed traders toward popular platforms where they can wager on everything from sports to politics, putting money on key Senate, House, and gubernatorial races across the United States. And right now, they're leaning blue.

Which races are drawing the biggest bets?

Individual contests are pulling serious volume of their own. The Los Angeles mayoral race, which will decide whether Democrat Karen Bass gets a second term, has drawn just shy of $110 million in trading volume.

Texas is hosting two of the platform's most active markets. The state's Senate race is nearing the $100 million mark, with traders giving Democrat James Talarico a 71% chance of defeating Republican Ken Paxton. But the blue bets stop at the governor's mansion: traders give incumbent Republican Greg Abbott a 65% chance of winning a gubernatorial contest that has drawn $21 million in volume. His challenger, Gina Hinojosa, is seeking to give Texas its first Democratic governor since 1995.

In short: Congress control drives the dollars, and single marquee races run a distant second.

How did prediction markets get here?

The surge builds on the industry's breakout moment in 2024, when traders on Kalshi and Polymarket favored Donald Trump as the winning candidate even as polls largely showed a toss-up. His victory helped turn the platforms into closely watched political barometers.

That barometer status now comes with real scrutiny.

How reliable are the odds?

The forecasting record has hit a few bumps, and recent misses have raised questions about how much faith to put in the numbers.

Last month, traders on Kalshi and Polymarket put their money on Flávio Bolsonaro, the son of former Brazilian President Jair Bolsonaro, to unseat incumbent Lula da Silva. They gave Bolsonaro roughly an 80% chance of winning the presidential runoff — before the odds swung toward Lula as the results rolled in.

Wisconsin delivered another curveball in August. Traders gave Francesca Hong roughly a 95% chance of winning the state's Democratic gubernatorial primary. Instead, David Crowley edged her out by less than half a percentage point. Polymarket later deleted a celebratory post touting Hong's odds, while Kalshi's founders defended the forecast with a reminder: "5% is not 0%."

That defense is mathematically fair, but it cuts both ways — the same logic applies to the 7% chance traders currently assign to Republicans holding the House.

With $1.4 billion already wagered, Tuesday's results will do more than decide Congress. They'll score the biggest test yet of whether prediction markets deserve their reputation as political crystal balls.