US midterm election contract trading $2 billion... Kalshi ahead of Polymarket

Trading volume in 2026 U.S. midterm election contracts reached $2 billion by November 4, with Kalshi accounting for $1.53 billion and Polymarket $474 million, according to a Prediction Frontier analysis. Roughly 75% of that volume came after October 20, a window that included a 44-hour data gap on October 19–20. Dune data show $573 million traded across the two platforms in the final week before the election, 4.2 times the prior week. In the 24 hours after U.S. markets closed on election day, volume hit $794 million, with Kalshi contributing $698 million. The concentration of activity in the closing stretch underscores how quickly prediction-market liquidity builds around a binary political event, and the post-election tally will show whether Kalshi's lead holds once settlement flows are counted.