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Prediction markets price Democratic House victory higher than the 80 percent forecast.

Action Network compared market prices with polls and forecasts on October 31, finding markets about 12 to 13 points more confident than Decision Desk HQ on House control. Senate control was closer, at 68 percent on both Polymarket US and Kalshi against 60 percent in the forecast model.

House markets show a wider gap with the forecast

Democrats’ chances of winning House control stood at 93 percent on Polymarket US and 92 percent on Kalshi, according to Action Network’s comparison of prediction markets, polls and forecasts on October 31.

Decision Desk HQ’s forecast model put the probability at 80 percent. That left the market-implied chances 13 percentage points higher on Polymarket US and 12 points higher on Kalshi—a larger difference than the comparison found for Senate control.

Senate pricing is closer to the model

For Senate control, Action Network reported probabilities of 68 percent on both Polymarket US and Kalshi, compared with 60 percent in the forecast model. The supplied summary does not identify which party those Senate probabilities refer to.

The comparison, published October 31, 2026, at 12:30 PM ET, shows the two platforms closely aligned with each other. Their House probabilities differed by just one percentage point, while their Senate probabilities matched; both sets of prices were above the corresponding model estimates.

What it means for prediction markets

  • The House is the larger point of divergence: Market prices put Democratic control 12 to 13 percentage points above Decision Desk HQ’s estimate.
  • Senate disagreement is narrower: The reported market probabilities exceeded the model by 8 percentage points.
  • Platform agreement is not model agreement: Polymarket US and Kalshi offered nearly identical readings, but both differed from the forecast benchmark.
KalshiPolymarketSenateInfiniti MarketsInfiniti Signals

Sources & attribution

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    Action Networkactionnetwork.com
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    https://www.actionnetwork.com
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