Sen. Jeff Merkley (D-OR) speaks at a news conference on his marathon overnight speech on the Senate floor at the U.S. Capitol Building on Oct. 22, 2025 in Washington, DC.

A group of congressional Democrats on Thursday introduced legislation that would ban prediction market bets on elections, government actions, war and sports, as scrutiny on the popular platforms intensifies.

Sens. Jeff Merkley, D-Ore., and Elizabeth Warren, D-Mass., and Rep. Jamie Raskin, D-Md., are leading the measure, which comes after a series of well-timed bets placed on world events — including the ousting of Venezuelan President Nicolas Maduro and the war in Iran — raised questions about prediction markets like Kalshi and Polymarket.

"When anyone can use prediction markets to make a well-timed bet on Congress passing a bill, government decisions, or a military strike, it's ripe for corruption and erodes public trust," Merkley said in a statement. "The STOP Corrupt Bets Act restores the original intent of prediction markets and prevents these markets from further eroding our democratic institutions and turning them into a casino."

The bill, which would impose broader limitations on the markets than most other legislative measures, is the latest in a flurry of proposals to rein-in prediction markets, which have exploded in popularity of late and allow users to place bets on a variety of events.