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.…