U.S. prediction markets favored Democrats to win control of both chambers of Congress as of October 27, 2026, one week before the midterm election. Republicans were defending their majorities in both the House and Senate.
Key Takeaways
- Kalshi traders put the chance of a Democratic sweep at 63%; Polymarket put it at 65%.
- Kalshi contracts also priced in a 29% chance of a Democratic House and Republican Senate.
- Prediction-market odds are not a substitute for political polls.
What prediction markets show
On Kalshi, the implied chance of Democrats winning both chambers had stayed relatively stable since the beginning of October. The platform also showed a just under 10% chance of Republicans retaining control of both.
Before early September, Kalshi traders had put the chance of a Democratic sweep below 50%. Earlier in the year, it was around 30%, before the start of the U.S.-Iran war and higher gas prices. The contracts resolve using official data from the U.S. Congress.
| Item | Details |
|---|---|
| Democrats win both chambers | 63% on Kalshi; 65% on Polymarket |
| Democrats win House; Republicans retain Senate | 29% on Kalshi |
| Republicans retain both chambers | Just under 10% on Kalshi |
How the odds differ from polls
Prediction markets reflect traders’ positions rather than the methods used in traditional political polling. A favored outcome remains uncertain: ahead of Brazil’s presidential election on October 25, markets gave high odds to right-wing candidate Flavio Bolsonaro, but incumbent President Lula da Silva was re-elected.
U.S. polls broadly showed Democrats favored in the national popular vote for the House and competitive in several Republican-state Senate races. House Speaker Mike Johnson, a Louisiana Republican, disputed the polling in a television appearance on October 26, saying it was inaccurate.
Next milestone
The midterm election is scheduled for November 3, 2026.
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Disclaimer
This FinanceVelix article provides general information, not personalized financial, investment, legal, or tax advice. Market prices, interest rates and economic conditions can change; investments carry a risk of loss. Facts reflect the material available when published and may change. Check important information independently and consult a qualified professional when needed. Mentioning an asset, company, or service is not an endorsement.
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