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 J.D. Vance win the 2028 Republican presidential nomination?
Vol $10K today · $16.3M total
Will Chuck Grassley be the Republican nominee for the Senate in Iowa?
Vol $23 today · $662 total
Both markets price this about the same, around 38%. Polymarket trades about 433.6× more volume today, so its price has more money behind it. They resolve on different dates (Nov 8 vs Nov 7), 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) | 39% | 38% |
| Change (24h) | +0.1 pt | +0.5 pt |
| Volume today | $10K | $23 |
| Total volume | $16.3M | $662 |
| Liquidity | $351.9K | — |
| Open interest | — | $622 |
| Resolves | 25mo | 37mo |
| Tracked for | 19 days | 16 days |
Resolution rules: read both before trusting a gap
Polymarket
This market will resolve to “Yes” if the named individual wins and accepts the 2028 nomination of the Republican Party for U.S. president. Otherwise, this market will resolve to “No”. The resolution source for this market will be a consensus of official Republican Party sources. Any replacement of the Republican nominee before election day will not change the resolution of the market.
Kalshi
If Chuck Grassley wins the nomination for the Republican Party to contest the 2028 Class III Iowa Senate seat, 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.