Senators Elizabeth Warren and John Curtis asked Kalshi and Polymarket in an October 28, 2026, letter how they prevent insider trading and manipulation in election markets. They requested written answers to seven questions by November 3; the letter does not establish how well either company’s safeguards work.
The senators asked how many suspected cases each firm had identified since January 1, how many trades were stopped before going through, and how many cases were referred to regulators or law enforcement. They also asked about trading by people with nonpublic information, independent reviews of surveillance systems, and safeguards planned before the elections. Kalshi said it prohibits insider trading and manipulation and blocks candidates and campaign staff from trading. Polymarket did not immediately respond to The Hill’s request for comment.
