Polymarket$2.32BOIOpen interest: sum of pool liquidity across all active markets, reported by the Polymarket API.
Kalshi$350.67MOIOpen interest: total contracts outstanding across all active markets, reported by the Kalshi API.
Limitless$18.48MOIOpen interest: estimated from total volume traded (USDC). Limitless does not report a separate OI metric.Compare KY-04 Republican Primary Winner prediction market odds side by side across Polymarket, Kalshi. Platforms currently disagree by an average of 2.6pp, with the largest spread reaching 5.9pp. These price differences can signal arbitrage opportunities or reflect different trader sentiment. With $27.9K in combined trading volume across 4 outcomes, this is one of the notable cross-platform prediction markets.
Ed GallreinPolymarketKalshiCost: 94¢ per pair → pays $1 at resolution. Gross spread 5.9pp before fees.
View all arbs| Outcome | Polymarket | Kalshi | Spread |
|---|---|---|---|
Thomas Massie | 66%-1.5 | 63%-5.0 | 2.5pp spread |
Ed Gallrein | 35%+1.5 |
| 5.9pp spread |
Robert Wells Jr. | 0%— | 1%±0 | 0.9pp spread |
Nicole Lee Ethington | 0%— | 1%±0 | 0.9pp spread |
