Kalshi and Polymarket price a 75% chance of a Democratic sweep, days after markets misjudged Brazil’s runoff. As Americans across the country head to the polls for the US midterm elections Tuesday, prediction market traders have spent months wagering on the outcome. According to an analysis by The Washington Post, nearly $1.9 billion in election-related contracts had traded on Kalshi and Polymarket as of Monday, marking record trading activity for a midterm election cycle.