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Polymarket’s higher Democratic odds yield better scores in midterm comparison

Before polls closed, Kalshi priced Democrats at 93.3 percent for the House and 75.0 percent for the Senate, against Polymarket at 94.5 percent and 75.5 percent, and Democrats won both. RotoWire put Polymarket's Brier score at 0.0030 for the House and 0.0600 for the Senate, against Kalshi at 0.0045 and 0.0625, with lower scores indicating better accuracy.

Polymarket recorded lower Brier scores than Kalshi for both chambers in the 2026 midterms, according to RotoWire. Both platforms favored Democrats before polls closed, and Democrats won the House and Senate.

How the forecasts compared

For the House, Kalshi assigned Democrats a 93.3 percent probability of winning, compared with 94.5 percent on Polymarket. RotoWire calculated a House Brier score of 0.0045 for Kalshi and 0.0030 for Polymarket.

The Senate forecasts were closer together: Kalshi priced a Democratic victory at 75.0 percent, while Polymarket put it at 75.5 percent. Their respective Senate Brier scores were 0.0625 and 0.0600, according to RotoWire.

A narrow advantage across two outcomes

Lower Brier scores indicate better accuracy. With Democrats winning both chambers, Polymarket’s slightly higher probabilities for those outcomes produced the better score in each comparison.

Both platforms also scored better on the House than on the Senate. Their pre-close probabilities reflected greater confidence in a Democratic House victory than in a Democratic Senate victory.

What it means for prediction markets

  • The distinction was in confidence, not direction: Both platforms favored the eventual winner in each chamber.
  • Polymarket led on the reported measure: Its Brier scores were lower for both the House and Senate.
  • The comparison is limited: These two chamber outcomes alone do not establish which platform is more accurate across other markets.
KalshiPolymarketSenateInfiniti MarketsInfiniti Signals

Sources & attribution

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    RotoWirerotowire.com
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    https://www.rotowire.com
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