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Senators warn prediction markets over election betting manipulation

The senators cited past incidents of candidates wagering on their own races and demanded safeguards by Tuesday.

By Elise Tremblay, Editor-in-Chief
October 31, 2026

U.S. senators Elizabeth Warren and John Curtis have written to the heads of prediction market platforms Kalshi and Polymarket, expressing alarm over potential manipulation in election betting. The bipartisan letter, sent to Kalshi CEO Tarek Mansour and Polymarket CEO Shayne Coplan, requests detailed information on their safeguards against insider trading and market abuse. The senators demanded a written response by Tuesday outlining past prevention measures, referrals to regulators and current protective steps. They specifically cited concerns about contracts tied to election outcomes.

"We write to express concerns about election related prediction markets and to request specific information about your companies’ efforts to prevent insider trading, market manipulation, and wagers based on material nonpublic information," Warren and Curtis wrote. Their letter referenced several instances where political candidates wagered on their own races on Kalshi in 2025 and 2026. It also mentioned alleged market manipulation on Polymarket during the 2024 presidential election. "These examples raise critical questions about how many election-related transactions have escaped detection," the senators stated.

The lawmakers pointed to a 2025 case described by the Commodity Futures Trading Commission where a candidate traded on his own candidacy. That activity was uncovered through social media videos before Kalshi issued a penalty. "Kashi’s own enforcement record demonstrates the problem with event contracts referencing elections and political candidates," the letter reads. Warren and Curtis asked what specific cases of election-related insider trading had been reported to the CFTC. "We remain skeptical that your companies can sufficiently police these event contracts with effective scrutiny and meaningful accountability," they concluded.

Former Virginia Democratic Senate candidate Mark Moran described his own contentious experience with Kalshi on a podcast. He said he placed a $100 bet on his own candidacy after the company added his name to a market. Kalshi initially proposed a one-year suspension and an $800 fine for this violation. When Moran refused to issue a public statement, the company increased the penalty to a five-year ban and a fine exceeding $6,200.

"I had to register with my own driver’s license, put my name to this, yet I was allowed to then bet," Moran said. "Why is this happening?" He objected to Kalshi's requirement that he publicly acknowledge the enforcement action, viewing it as an attempt to control his narrative. According to Kalshi's account, its compliance department found Moran placed two trades and promoted the market on social media on January 27, 2026, violating its rules. The company said Moran admitted the trades were improper in a call the next day but later refused to settle and stopped responding to correspondence. The senators' letter arrives as congressional scrutiny of election prediction markets intensifies ahead of the upcoming election. They asked the companies to detail their past prevention efforts and any referrals made to the CFTC.