Kalshi midterm trading tops $1.4bn as traders bet on Democratic sweep

The surge in activity, reported by Fortune, has been led by a contract on which party will control Congress, which has drawn $251 million in trading volume. A similar contract on House control has crossed $181 million, while a market tracking all possible combinations of House and Senate control has topped $112 million.

Among individual races, the Los Angeles mayoral contest has attracted nearly $110 million, and the Texas Senate race is nearing $100 million, where traders give Democrat James Talarico a 71% chance of defeating Republican Ken Paxton. However, in the Texas governor’s race, traders give incumbent Republican Greg Abbott a 65% chance of winning over Democrat Gina Hinojosa, who is seeking to become the state’s first Democratic governor since 1995.

The midterm trading builds on prediction markets’ breakout moment in 2024, when traders on Kalshi and Polymarket correctly favoured Donald Trump as the winning candidate even as polls showed a close race. That victory helped turn the platforms into closely watched political barometers. But the platforms have also recorded notable misses. Last month, traders gave Flávio Bolsonaro roughly an 80% chance of winning Brazil’s presidential runoff, before the odds swung toward incumbent Lula da Silva as results came in. In August, Wisconsin’s Democratic gubernatorial primary saw traders give Francesca Hong roughly a 95% chance of winning, but 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%.”