Forecasting 2026 Congressional Control: A Comparison of IEM and Kalshi Prediction Markets

Abstract

We report Iowa Electronic Markets (IEM) and Kalshi prediction market forecasts for the congressional control configuration resulting from the 2026 U.S. midterm elections.Both exchanges run separate markets on House and Senate control.Both indicate the most likely outcome is Democratic House control, but split on Senate control.Each exchange also runs a joint control market across the two chambers.In both markets, the most likely outcome has shifted from a Democratic House and Republican Senate to Democratic control of both chambers.Vector autoregressions show that neither market consistently leads the other in dayto-day price changes.IEM prices exhibit no significant momentum or reversal, consistent with efficient pricing.Kalshi prices sometimes display momentum, consistent with the presence of large-scale hedgers, speculators, and/or momentum traders attracted by Kalshi's scale and liquidity, but seemingly absent from the investment-capped IEM.