Polymarket vs. Kalshi
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See where the two biggest prediction markets disagree. Pick any two markets, or start from the biggest gaps below: prices, volume, history and the resolution rules, side by side.
Will the Republican Party hold exactly 54 Senate seats after the 2026 midterm elections?
Vol $14.4K today · $817.1K total
Will the Democratic party hold exactly 54 Senate seats in the 121st Congress?
Vol $117 today · $8K total
Kalshi is 5 points higher than Polymarket (8% vs 2%). Polymarket trades about 122.3× more volume today, so its price has more money behind it. They resolve on different dates (Nov 3 vs Feb 1), so they may not be exactly the same bet.
History starts when we first saw each market, so a newly added market has a short line.
| Polymarket | Kalshi | |
|---|---|---|
| Probability (Yes) | 2% | 8% |
| Change (24h) | +0.5 pt | +0.0 pt |
| Volume today | $14.4K | $117 |
| Total volume | $817.1K | $8K |
| Liquidity | $284K | — |
| Open interest | — | $7.7K |
| Resolves | 9d | 28mo |
| Tracked for | 14 days | 16 days |
Resolution rules: read both before trusting a gap
Polymarket
This market will resolve according to the Republican Party’s seat count in the United States Senate as a result of the 2026 United States midterm election scheduled for November 3, 2026. The seat count includes all regular and special Senate elections that determine representation in the upcoming 120th Congress and are scheduled to take place in November 2026 as of October 31, 2026. Runoffs for qualifying elections will determine attribution of the relevant seat, even if they take place after November 2026. Vacant seats for which no election or special election to fill the seat is scheduled to take place in November 2026 as of October 31, 2026 will be treated as held by the party affiliation of the most recent member to hold that seat. For seats contested in the specified election, seats are attributed to the party under which the member was elected. If a member-elect changes party affiliation, or vacates their seat, between election day and the formal organization of Congress, the seat is attributed to the party under which the member was elected. For seats not contested in the specified election, seats are attributed to the party that holds the seat as of the date of the election. If a current sitting member of the U.S. Senate who is not up for election changes party affiliation or vacates their seat after the date of the election, the seat is attributed to the party und…
Kalshi
If the Democratic party has exactly 54 Senate seats on Feb 1, 2029, then the market resolves to Yes.
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Informational only — not financial advice. Odds are mirrored from each platform and may lag the live order book.