Calls are growing inside Congress for a formal investigation of Polymarket after another instance of anonymous traders making well-timed, well-sized bets on a major geopolitical event hours before it became public. The pattern is becoming hard to ignore: someone, somewhere, keeps knowing things before markets — or media — do.

Prediction markets have always carried this tension. Their theoretical value is as an information aggregation mechanism, surfacing the collective probability estimates of informed participants. The problem is that some participants are more informed than others, and not always because they’re better analysts. When bets arrive in size, in the right direction, in the hours before an event breaks, the question of whether markets are discovering truth or laundering inside information becomes unavoidable. Congress investigating Polymarket is probably not the most efficient path to an answer. But it may be the one that actually happens.