Kalshi and Polymarket prices on the same 2026 midterm race differ by just 1.1 points on average.
That is the gap on the favorite’s win probability across 49 races priced on both exchanges at 8 PM ET on October 14, 2026. In the most-traded races it is 1.2 points. Adding PredictIt, the average spread between the highest and lowest of the three venues is 2.0 points, and they are furthest apart in New Hampshire Senate.
Daily history since July 1, 2026; three-venue snapshot taken Oct 15, 2026, 7:39 AM ET. Updated daily until Election Day.
By Arthur Angelo, PredictionScout Research · Updated Oct 15, 2026, 7:46 AM ET
Key findings
- The two big exchanges mostly agree. On October 14, the median gap across 49 races was 1.0 point and the average 1.1. 0 races were 5 or more points apart. In the 32 most-traded races the average was 1.2 points.
- The gap has narrowed since summer. Monthly average of the daily index: July 2.1, August 1.8, September 1.4, October 1.2 points. Fewer races were listed on both exchanges in July (16 on July 1 vs 49 now), so early months rest on fewer races.
- Widest Kalshi–Polymarket gap today: Maine Senate, 3.0 points on Troy Jackson (D) (Kalshi 56.5%, Polymarket 59.5%).
- PredictIt is most often the odd one out. In 28 of the 59 races all three venues price, PredictIt is the furthest from the other two. Average pairwise gaps: Kalshi–Polymarket 0.9, Kalshi–PredictIt 1.6, Polymarket–PredictIt 1.6 points.
The gap index, day by day
Every race, today
Live midpoint prices from the snapshot taken Oct 15, 2026, 7:39 AM ET. The gap columns are in percentage points on the favorite. Click a race for its full odds page.
| Race | Favorite | Kalshi | Polymarket | PredictIt | Kalshi–Polymarket gap | Widest gap (3 venues) | Liquid |
|---|---|---|---|---|---|---|---|
| New Hampshire Senate | Chris Pappas (D) | 89.5% | 88.5% | 84.5% | 1.0 | 5.0 | Yes |
| Florida Senate | Ashley Moody (R) | 91.5% | 90.5% | 86.5% | 1.0 | 5.0 | Yes |
| Wisconsin governor | David Crowley (D) | 80.5% | 81.0% | 76.0% | 0.5 | 5.0 | Yes |
| South Carolina Senate | Darline Graham (R) | 85.5% | 84.5% | 80.5% | 1.0 | 5.0 | Yes |
| Michigan governor | Jocelyn Benson (D) | 93.8% | 95.2% | 91.0% | 1.4 | 4.1 | Yes |
| Iowa governor | Rob Sand (D) | 88.5% | 90.5% | 86.5% | 2.0 | 4.0 | Yes |
| Alabama governor | Tommy Tuberville (R) | 93.4% | 94.2% | 90.5% | 0.8 | 3.7 | No |
| Maine Senate | Troy Jackson (D) | 56.5% | 59.5% | 56.0% | 3.0 | 3.5 | Yes |
| Kansas Senate | Roger Marshall (R) | 63.5% | 62.5% | 60.0% | 1.0 | 3.5 | Yes |
| Minnesota governor | Amy Klobuchar (D) | 95.2% | 95.5% | 92.0% | 0.3 | 3.5 | No |
| Colorado Senate | John Hickenlooper (D) | 98.8% | 98.0% | 95.5% | 0.8 | 3.3 | No |
| Maryland governor | Wes Moore (D) | 97.4% | 97.8% | 94.5% | 0.4 | 3.3 | No |
| Wyoming Senate | Harriet Hageman (R) | 98.6% | 98.4% | 95.5% | 0.2 | 3.1 | No |
| Iowa Senate | Ashley Hinson (R) | 58.5% | 58.5% | 55.5% | 0.0 | 3.0 | Yes |
| Ohio Senate | Sherrod Brown (D) | 59.5% | 61.5% | 62.5% | 2.0 | 3.0 | Yes |
| Ohio governor | Amy Acton (D) | 68.5% | 71.5% | 70.0% | 3.0 | 3.0 | Yes |
| Nevada governor | Aaron Ford (D) | 52.5% | 52.0% | 55.0% | 0.5 | 3.0 | Yes |
| Louisiana Senate | Julia Letlow (R) | 94.6% | 93.5% | 92.0% | 1.1 | 2.6 | No |
| Minnesota Senate | Peggy Flanagan (D) | 86.5% | 87.5% | 85.0% | 1.0 | 2.5 | Yes |
| Nebraska Senate | Pete Ricketts (R) | 74.5% | 72.5% | 72.0% | 2.0 | 2.5 | Yes |
| Kentucky Senate | Andy Barr (R) | 96.2% | 96.8% | 94.5% | 0.7 | 2.3 | No |
| Alabama Senate | Barry Moore (R) | 98.3% | 97.4% | 96.0% | 0.9 | 2.3 | No |
| Senate control | Democrat | 61.5% | 63.5% | 63.5% | 2.0 | 2.0 | Yes |
| Michigan Senate | Abdul El-Sayed (D) | 68.5% | 70.5% | 69.0% | 2.0 | 2.0 | Yes |
| Georgia governor | Rick Jackson (R) | 51.5% | 50.0% | 52.0% | 1.5 | 2.0 | Yes |
| Alaska Senate | Mary Peltola (D) | 73.5% | 73.6% | 75.5% | 0.1 | 2.0 | Yes |
| Vermont governor | Phil Scott (R) | 76.5% | 75.0% | 77.0% | 1.5 | 2.0 | Yes |
| Rhode Island governor | Helena Foulkes (D) | 95.2% | 97.0% | 95.5% | 1.8 | 1.8 | No |
| New Mexico Senate | Ben Ray Luján (D) | 97.2% | 97.2% | 95.5% | 0.1 | 1.7 | No |
| House control | Democrat | 90.3% | 90.5% | 89.0% | 0.2 | 1.5 | Yes |
| Arizona governor | Katie Hobbs (D) | 88.5% | 88.5% | 87.0% | 0.0 | 1.5 | Yes |
| Colorado governor | Phil Weiser (D) | 96.0% | 96.8% | 97.5% | 0.7 | 1.5 | No |
| Arkansas Senate | Tom Cotton (R) | 94.0% | 94.4% | 93.0% | 0.4 | 1.4 | No |
| New Jersey Senate | Cory Booker (D) | 96.6% | 97.5% | 98.0% | 0.9 | 1.4 | No |
| Oregon Senate | Jeff Merkley (D) | 97.8% | 97.9% | 96.5% | 0.1 | 1.4 | No |
| South Dakota Senate | Mike Rounds (R) | 95.2% | 94.1% | 95.5% | 1.2 | 1.4 | No |
| Massachusetts governor | Maura Healey (D) | 95.1% | 96.0% | 96.5% | 0.9 | 1.4 | Yes |
| North Carolina Senate | Roy Cooper (D) | 95.2% | 95.8% | 94.5% | 0.6 | 1.3 | Yes |
| Virginia Senate | Mark Warner (D) | 97.4% | 97.8% | 96.5% | 0.4 | 1.3 | No |
| Tennessee Senate | Bill Hagerty (R) | 94.6% | 95.8% | 95.0% | 1.2 | 1.2 | No |
| Connecticut governor | Ned Lamont (D) | 95.4% | 96.6% | 96.0% | 1.2 | 1.2 | No |
| New York governor | Kathy Hochul (D) | 94.3% | 95.2% | 94.0% | 0.9 | 1.2 | Yes |
| Georgia Senate | Jon Ossoff (D) | 95.2% | 96.1% | 95.0% | 0.9 | 1.1 | Yes |
| Texas Senate | James Talarico (D) | 63.5% | 62.5% | 62.5% | 1.0 | 1.0 | Yes |
| Montana Senate | Kurt Alme (R) | 92.5% | 93.5% | 92.5% | 1.0 | 1.0 | Yes |
| Balance of power | D sweep | 61.5% | 62.5% | 62.5% | 1.0 | 1.0 | Yes |
| California governor | Xavier Becerra (D) | 95.8% | 96.4% | 95.5% | 0.6 | 0.9 | Yes |
| Idaho Senate | Jim Risch (R) | 94.6% | 95.3% | 95.5% | 0.7 | 0.9 | Yes |
| Illinois Senate | Juliana Stratton (D) | 97.6% | 98.4% | 98.5% | 0.8 | 0.9 | No |
| Oklahoma Senate | Kevin Hern (R) | 97.2% | 97.8% | 97.0% | 0.6 | 0.8 | No |
| Pennsylvania governor | Josh Shapiro (D) | 98.2% | 97.7% | 97.5% | 0.5 | 0.7 | No |
| New Mexico governor | Deb Haaland (D) | 93.1% | 93.0% | 92.5% | 0.1 | 0.6 | No |
| Texas governor | Greg Abbott (R) | 77.5% | 78.0% | 77.5% | 0.5 | 0.5 | Yes |
| Florida governor | Byron Donalds (R) | 79.5% | 79.5% | 80.0% | 0.0 | 0.5 | Yes |
| Massachusetts Senate | Ed Markey (D) | 98.0% | 98.4% | 98.5% | 0.4 | 0.5 | No |
| Rhode Island Senate | Jack Reed (D) | 98.0% | 98.0% | 97.5% | 0.0 | 0.5 | No |
| Delaware Senate | Democrat | 98.5% | 98.1% | 98.5% | 0.4 | 0.4 | No |
| Mississippi Senate | Cindy Hyde-Smith (R) | 90.7% | 91.0% | 91.0% | 0.3 | 0.3 | Yes |
| West Virginia Senate | Shelley Moore Capito (R) | 98.0% | 98.0% | 98.0% | 0.0 | 0.0 | No |
| Tennessee governor | Marsha Blackburn (R) | 93.5% | 95.6% | — | 2.0 | 2.0 | No |
| Maine governor | Hannah Pingree (D) | 94.1% | 95.5% | — | 1.4 | 1.4 | No |
| Oklahoma governor | Mike Mazzei (R) | 90.7% | 89.5% | — | 1.2 | 1.2 | No |
| Hawaii governor | Josh Green (D) | 98.1% | 99.2% | — | 1.1 | 1.1 | No |
| Arkansas governor | Sarah Huckabee Sanders (R) | 96.0% | 97.0% | — | 1.0 | 1.0 | No |
| Oregon governor | Tina Kotek (D) | 74.5% | 75.5% | — | 1.0 | 1.0 | No |
| Idaho governor | Brad Little (R) | 97.0% | 97.8% | — | 0.7 | 0.7 | No |
| Illinois governor | JB Pritzker (D) | 97.1% | 97.7% | — | 0.6 | 0.6 | No |
| Wyoming governor | Eric Barlow (R) | 97.2% | 97.8% | — | 0.5 | 0.5 | No |
| South Carolina governor | Alan Wilson (R) | 94.7% | 94.5% | — | 0.2 | 0.2 | No |
| South Dakota governor | Larry Rhoden (R) | 97.4% | 97.6% | — | 0.2 | 0.2 | No |
Download the data
Daily index and race-level gaps (CSV)
One row per race per day with the Kalshi and Polymarket price of the favorite and the gap, plus the three-venue prices from each daily snapshot. Free to reuse under CC BY 4.0.
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Methodology
- Races. Every 2026 Senate, governor and chamber-control market tracked on our midterms tracker that both Kalshi and Polymarket list. Candidates are grouped by party, so a race’s price is the party’s chance of winning it. PredictIt long-shot contracts with no bids at all are left out, because PredictIt shows them at 1¢ and a dozen of them would add 10+ points to a party’s total.
- The gap. For each race we find the favorite (the party with the highest average price across the venues) and take the absolute difference between the venues’ prices for it, in percentage points. The index is the average across races. We also report the median, because a few thin races can pull the average up.
- Daily history. A race is left out on any day when either exchange’s candidate prices add up to less than 85% or more than 115%, which happens when a candidate’s market had not opened yet or had no quotes. Kalshi: the hourly candle ending at 8 PM ET, midpoint of bid and ask when the spread is 10¢ or less, otherwise the last trade. Polymarket: its public daily price history point at the same time. A race enters the history once both exchanges have prices for it.
- Three-venue view. PredictIt does not publish a price history through its public API, so its prices come from our daily snapshots of all three venues (morning, live bid/ask midpoints). The three-venue numbers start on October 1, 2026.
- Liquid races. At least 100,000 Kalshi contracts traded and $100,000 of Polymarket volume, as of the latest snapshot.
- Why gaps exist. The venues have different users, fees, position limits and ways to deposit money, and moving money between them takes time. PredictIt also caps how much each trader can hold in a contract. A gap is not a guaranteed profit: fees, spreads and the time until settlement all eat into it.
Cite this research
Suggested citation: PredictionScout. (2026, October 15). Prediction Market Price Gap Index: Kalshi vs Polymarket vs PredictIt. https://predictionscout.com/research/prediction-market-price-gap-index/
For a chart or news story: “Source: PredictionScout analysis of public exchange data (https://predictionscout.com/research/prediction-market-price-gap-index/)”
The data and charts on this page are free to reuse under CC BY 4.0 with a link back to this page. Underlying data: Kalshi, Polymarket and PredictIt public APIs.
Data sources: prices and volumes come from the public APIs of Kalshi and Polymarket, and PredictIt. All trademarks belong to their owners. PredictionScout is independent and not affiliated with any exchange. Nothing here is investment, betting, or legal advice.
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