‘Death Markets’ and Attack Ads: Prediction Rivalry Turns Nasty

Kalshi Inc. and Polymarket are slinging weighty accusations at each other as the prediction market rivalry heats up and the nascent industry comes under intense scrutiny in Washington.

While the platforms have sparred frequently in the past, the rhetoric has escalated in recent days after Kalshi launched a pointed advertising campaign and its employees publicly criticized Polymarket.

“Polymarket’s irresponsible, dangerous, and illegal behavior threatens legal American prediction markets,” Benjamin Freeman, who works on political and election markets at Kalshi, wrote in a social media post on Monday.

A Kalshi advertisement at a bus stop in Washington in March.

Photographer: Daniel Heuer/Bloomberg

The accusations quickly sparked a heated back-and-forth between the companies.

“We welcome ...