David Yaffe-Bellany and William K. RashbaumJul 21, 2026 – 12.00pmEarly one morning in November 2024, Shayne Coplan, the founder of Polymarket, awoke to an unexpected visit. A group of FBI agents burst into his New York apartment with a battering ram, scouring for evidence of illegal betting on his platform.On social media, Coplan dismissed the raid as a politically motivated attack by the Biden administration. But privately, he and his advisers voiced suspicions about a different culprit, whom they blame for many of Polymarket’s problems: Tarek Mansour, the chief executive of Kalshi, Coplan’s biggest rival in the booming business of prediction markets.Subscribe to gift this articleGift 5 articles to anyone you choose each month when you subscribe.Subscribe nowAlready a subscriber? Fetching latest articles
Do these CEOs loathe each other? Bet on it
Shayne Coplan of Polymarket and Tarek Mansour of Kalshi are young billionaires intent on dominating prediction markets. It’s more than a battle. It’s “bad blood.”
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