Prediction Markets Face Midterm Test as Polls Give Democrats Higher Odds

Prediction markets and polling organizations both see Democrats as favored to win both chambers in Tuesday’s U.S. midterm elections, but prediction markets assign lower odds, particularly for the Senate. According to Sina Finance, citing Yahoo Finance’s analysis, prediction markets gave Democrats a 73.1% chance of winning the Senate as of Monday, compared with 80.3% from polling models. For the House, the figures were 94.1% and 96.7%, respectively. The comparison averages daily probabilities from Kalshi, Polymarket, and PredictIt and compares them with Nate Silver’s model and Harvard University’s ElectIt model. Kalshi said trading volume in midterm-related contracts had exceeded $1.2 billion, surpassing the platform’s volume during the 2024 presidential election. Sen. Elizabeth Warren and Republican Sen. John Curtis have raised concerns with Kalshi and Polymarket about election-related contracts and potential market manipulation. Kalshi has also sued in Utah over whether federal rules override state anti-gambling laws; the nonprofit Better Markets filed a court brief supporting Utah’s position.