Press note
Polymarket vs Kalshi Midterm Odds: 65 Matched Contracts and What a $50,000 Bet Moves
65Midterm contracts matched across the venues
House control, Senate control and 31 Senate races, prices read 18:52–18:53 UTC on 12 September 2026
Vultax matched 65 midterm contracts across Polymarket and Kalshi. The venues usually sit 1 to 3 points apart, Polymarket prices Democrats higher in 15 of the 18 most-traded outcomes, and $50,000 on a Democratic Senate cost 1.0¢ above the price on Kalshi and 2.4¢ on Polymarket. Polymarket and Kalshi mostly agree on the 2026 midterms. Across 65 contracts that exist on both venues, from control of each chamber to 31 individual Senate races, the median pair's daily prices sat 1.4 points apart over the last 30 days. On the questions that matter most on 12 September, they told the same story: Democrats around 85 to 87 cents to win the House, the Senate a coin flip, Texas and Ohio close, Maine and Michigan leaning Democratic.
Observed 2026-08-13 to 2026-09-12, population: 15 of 65 matched midterm contract pairs.
Supporting figures
- 1.4 pts — Typical daily gap, 30 days to 12 SeptemberMedian across 65 pairs of the average absolute difference between the venues' daily prices
- 319 of 379 — Days Polymarket priced a Democratic House higherDaily prices since 9 August 2025; the average difference was 1.85 points
- 1.0¢ / 2.4¢ — $50,000 on a Democratic Senate, above the priceKalshi against Polymarket, median over 58 readings, 12–13 September 2026; both filled in every reading
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- Every published table and chart, with units and sources
- Open the 2026 midterms room
- Senate, House and governor races priced live on Polymarket, with control odds, seat math and the day's biggest movers.
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How to cite
Vultax Research, Polymarket vs Kalshi Midterm Odds: 65 Matched Contracts and What a $50,000 Bet Moves, 2026-09-16, https://vultax.com/research/polymarket-vs-kalshi-midterms-odds-2026
Published 2026-09-16. Figures are the published study; live screens move. Plain-text version · Use our data