US Senators Press Kalshi, Polymarket to Disclose Election Insider-Trading Safeguards
Summary
- Two U.S. senators said they had asked Kalshi and Polymarket to disclose their systems for preventing insider trading tied to elections.
- They said specific cases had emerged in the two platforms’ election prediction markets, including candidates betting directly and the possibility of market manipulation.
- Kalshi said it is using trading restrictions and a market integrity committee, while Polymarket said it is investigating midterm-election bets and making CFTC referrals.
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Two U.S. senators have urged prediction-market platforms Kalshi and Polymarket to disclose their safeguards against insider trading in election-related markets.
Bitcoin.com reported on October 30 that Democratic Senator Elizabeth Warren and Republican Senator John Curtis sent a letter to Kalshi Chief Executive Officer Tarek Mansour and Polymarket Chief Executive Officer Shayne Coplan, asking them to answer seven questions about measures to prevent insider trading and market manipulation in election prediction markets. The response deadline is November 3, the day of the midterm elections.
In the letter, the senators said election-related event contracts are of particular concern because they are viewed as a gauge of political momentum. The questions covered how the platforms block trading by people with nonpublic information, including candidates, campaign staff and polling firms, and what systems they use to detect manipulation, including attempts to trade through third-party accounts.
The letter also cited specific cases at Kalshi. In May 2025, a video circulated on social media showing a candidate betting directly on his own candidacy contract. Kalshi fined the candidate and suspended that person from the platform for five years. Kalshi later disclosed three additional similar cases. For Polymarket, the senators cited a 2024 Fortune report saying roughly one-third of trading volume in presidential election prediction markets may have been most affected by wash trading.
The senators wrote that the detection of some improper trades does not mean the market is adequately protected. They also expressed skepticism about whether the two platforms can effectively police election contracts on their own.
Kalshi said it blocks trading by candidates and campaign staff using Federal Election Commission payroll data and has established an independent market integrity committee. Polymarket is investigating dozens of bets tied to the midterm elections and has reportedly referred at least two of them to the Commodity Futures Trading Commission.
Doohyun Hwang
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