Midterm Election Betting Tops $220M On Kalshi, Polymarket

Betting on the 2026 US midterm elections has surged on prediction markets Polymarket and Kalshi, with traders wagering more than $220 million so far this cycle, more than double the $92 million bet across the entire 2024 congressional cycle, according to a new Reuters analysis.

The figures come from the Anti-Corruption Data Collective (ACDC), a Washington-based research group that examined more than 21,000 markets covering the 2026 congressional midterms across Kalshi and Polymarket's US and international platforms through September 30, compared with 463 markets tracked for the 2024 cycle. 

ACDC found that both the number of election markets and the level of detail in each race's contracts have grown sharply since 2024, the cycle in which the two platforms first drew wide attention for correctly signaling Donald Trump's path back to the presidency.

Integrity Concerns Running Alongside The Growth

The binary "yes/no" contracts let traders bet on outcomes ranging from which party controls Congress to individual race winners and even when a candidate might drop out. That growth has drawn scrutiny from policymakers and advocacy groups who worry the markets could blur incentives around the integrity of elections or open new paths for insider trading. 

Kalshi has suspended a handful of candidates from sports betting on their own races, and public broadcaster NPR reported in May that campaign staffers had also placed bets on races they were working on.

Both platforms say their markets are closely monitored. A Kalshi spokesperson said its data is "bottom-up, not elites-driven," while a Polymarket spokesperson said its election markets have shown 98% accuracy one day out from a vote and that the platform uses dedicated surveillance systems built for political contracts. Kalshi also blocks election trades by politicians and campaign staff.

Public Opinion Still Runs Against It

Despite the platforms' growth, a Reuters/Ipsos poll published this week found most Americans oppose using prediction markets to wager on elections at all. 

Michelle Kendler-Kretsch of ACDC said the format "focuses a disruptive new financial technology on our democratic process," underscoring the gap between trading volume and public comfort with the practice as the midterms approach.