WASHINGTON (AP) — As the United States was preparing a daring mission to rescue an airman whose fighter jet was shot down by Iran, there was money to be made.

Users on Polymarket, the world’s largest prediction market, could place bets on when the airman would be rescued. When Rep. Seth Moulton, D-Mass., shared a screenshot of the activity on social media, an April 3 rescue was trading at 15% compared with 63% who were betting on April 4.

After Moulton posted the screenshot and blasted this “dystopian death market,” Polymarket stopped the betting, saying the market “does not meet our integrity standards.”

A confrontation is brewing in Washington over prediction markets, the online exchanges that allow users to bet on the outcome of everything from a baseball game to when Jesus Christ will return.

In a highly polarized Congress, the need to guard against the prediction markets being used for insider trading has become rare common ground. Members of both parties pressed the leader of a typically low-profile regulatory agency on the issue during a hearing. The market debate is also drawing in the White House, potential presidential candidates and state leaders.

“It’s a national conversation about what it means to have market integrity,” said Kristin Johnson, a former commissioner at the Commodity Futures Trading Commission, which regulates prediction markets in the U.S.

The markets, which include Polymarket and its chief rival Kalshi, have been criticized for everything from undermining the integrity of sports to contributing to an online betting addiction crisis among young men.

The Associated Press reported this month that a group of new accounts on Polymarket made highly specific, well-timed bets on whether the U.S. and Iran would reach a ceasefire on April 7, resulting in hundreds of thousands of dollars in profits for these new customers.

Polymarket officials say little publicly and didn’t comment for this story. The market, founded in 2020, operates largely offshore with limited functions in the U.S. that were allowed only after President Donald Trump returned to office.

Kalshi, meanwhile, says it already bans many of the most extreme betting markets and welcomes regulation.