Michael Selig, President Donald Trump's nominee to serve as Commodity Futures Trading Commission chairman, testifies in a Senate Agriculture Committee hearing on his nomination on Capitol Hill, Nov. 19, 2025.

Jonathan Ernst | Reuters

A group of Democratic lawmakers is urging the Commodity Futures Trading Commission to issue a rule that would aim to rein-in prediction markets, curb insider trading and prohibit certain types of event contracts.

In a letter first shared with CNBC and sent to the CFTC on Thursday, a group of congressional Democrats led by Jeff Merkley of Oregon., called on the federal agency to address "the rapid erosion of integrity" within prediction markets such as Kalshi and Polymarket.

"We strongly encourage you to use your authority to preserve the intent of prediction markets, and congressional intent behind the Commodity Exchange Act, by issuing a rule that prevents insider trading and corruption in the market and prohibits event contracts on the outcome of elections, war and…