Kalshi prematurely settled a Michigan vs. Western Michigan market, paying $18.6M to the wrong side before a last-second touchdown, then reversed the payouts.
LeBron James partners with Polymarket, a prediction market platform, announcing a full reveal on Tuesday.
Kalshi will not allow betting on whether its legal dispute with New Jersey reaches the Supreme Court, citing principle.
Donald Trump Jr.'s venture firm 1789 Capital is investing $300 million in Polymarket, adding to his advisory role and equity in rival Kalshi.
Kalshi suspended GOP candidate Laurie Buckhout for three years for betting on her own race, with a fine exceeding her wager.