What Two Betting Markets Say About the Midterms

Econbrowser reads the midterm odds off two prediction markets. On Polymarket, the sharp deterioration in Republican odds for holding the Senate occurred almost immediately after the beginning of the US-Iran War, and the first reversal between Republican and Democratic odds is dated to March 15. Kalshi put the odds of Democratic control of both houses at 59 percent. Two cautions come free with the numbers. Timing is not causation — a market can reprice for several reasons at once, and the start of a war is exactly the kind of moment when many things move together. And the two venues are not answering the same question: one is about the Senate majority, the other about both chambers.