A betting industry that has grown exponentially over the past two years is facing increasing scrutiny over a series of alleged insider trading scandals that have rocked congressional races and recently led to the arrest of a U.S. soldier. Last week, Gannon Ken Van Dyke was indicted after betting on the mission to capture former Venezuelan leader Nicolás Maduro. The Army soldier was accused of using his advance knowledge of the mission to place bets on Polymarket, a prediction market that allows users to trade on the likelihood of real-world events occurring. That same week, Polymarket’s competitor Kalshi fined and suspended three congressional candidates after the men allegedly placed bets on the outcome of their own elections....