US Senators Press Kalshi, Polymarket to Disclose Election Insider-Trading Safeguards
Summary
- US senators said they had asked Kalshi and Polymarket to disclose their systems for preventing election-related insider trading and market manipulation.
- In the letter, the senators asked the two platforms to answer seven questions about their election prediction markets, including how they block trading by holders of nonpublic information and detect circumvention through third-party accounts.
- The senators were skeptical about the two platforms' ability to self-regulate despite the detection of some improper trades, and the letter also cited internal sanctions and investigation and reporting cases at Kalshi and Polymarket.
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Two US senators have urged prediction-market platforms Kalshi and Polymarket to disclose their safeguards against election-related insider trading.
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 CEO Shayne Coplan, asking them to answer seven questions about measures to prevent insider trading and market manipulation in election prediction markets. The deadline for a response is November 3, the day of the midterm elections.
In the letter, the senators wrote that election event contracts are especially concerning because they are viewed as a gauge of political momentum. The questions included how the platforms block trading by people with nonpublic information, such as candidates, campaign staff and polling firms, and what systems they use to detect manipulation through trades routed via third-party accounts.
The letter also cited a specific case involving 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 him from the platform for five years. It later disclosed three more similar cases. Regarding Polymarket, the senators cited a 2024 Fortune report that said roughly one-third of trading volume in the presidential prediction market may have been driven by the most active traders.
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 self-regulate election contracts.
Kalshi said it blocks trading by candidates and campaign staff using payroll data from the Federal Election Commission and has established an independent market integrity committee. Polymarket is investigating dozens of midterm election-related bets, and at least two of them have reportedly been referred to the Commodity Futures Trading Commission.
