November 8, 2026 — Arbitrage windows between Kalshi and Polymarket widened sharply this week as traders repositioned ahead of the December FOMC meeting and recalibrated odds in several high-volume political and sports contracts. Spreads of 3 to 6 cents are showing on markets that typically close inside 1 to 2 cents, creating setups that reward patient capital willing to hold until resolution or convergence.
Below is a breakdown of the cleanest opportunities we’re tracking, along with the structural reasons they exist and what could close them this week.
Fed December Rate Cut: 4-Cent Spread Between Platforms
The headline opportunity this week sits on the December 10 FOMC decision. Kalshi’s “Fed cuts rates in December 2026” market is pricing a 25bp cut at 71%, while Polymarket’s equivalent contract sits at 67%. The 4-cent gap is the widest we’ve seen on a major monetary policy contract since early October and reflects a familiar pattern: Kalshi’s US-regulated book skews slightly more hawkish-reaction-sensitive, while Polymarket’s international liquidity has been fading the probability since last Wednesday’s softer-than-expected PPI print.
The clean arbitrage: buy YES at 67 on Polymarket and NO at 29 on Kalshi (implied 71% YES). Combined cost is 96 cents on a dollar of exposure, locking in a guaranteed 4-cent return at resolution regardless of outcome. Factor in a small transaction haircut and roughly 32 days of capital lockup, and the annualized return clears 45%.
What could close it: a single hawkish Fed speaker between now and the blackout period, or a hot CPI print on November 13, would snap Polymarket closer to Kalshi within hours.
Senate Control Decided in December Runoffs
The Louisiana and Mississippi Senate runoff markets have been bouncing since the general election, and liquidity thinned over the weekend as the political trading desk crowd moved on. That has left a 3-cent dislocation on the “Republicans hold Senate majority” contract: Kalshi at 82%, Polymarket at 79%.
Both figures broadly agree the GOP holds, but the gap exists because Polymarket is pricing in a non-trivial tail risk on the Mississippi contest where a late polling shift has not yet fully registered on Kalshi. The arbitrage pays 3 cents on a dollar, with resolution by December 14. Annualized this clears 30% net of fees. The main risk is correlated settlement timing if a runoff is contested or delayed.
Bitcoin Year-End: Kalshi Lags the Crypto Flow
On “Bitcoin closes above $110,000 on December 31,” Polymarket sits at 58% while Kalshi is quoting 52%. The 6-cent spread is the widest on a crypto contract this quarter and reflects the structural reality that Polymarket attracts the dedicated crypto-native flow while Kalshi’s user base is more diversified across macro and politics.
A YES/NO arbitrage here is cleaner than usual because both markets settle to the same CoinMarketCap index at UTC midnight on December 31. Buy NO on Polymarket at 42, YES on Kalshi at 52, lock in 6 cents for 53 days of capital. That annualized return is north of 75% assuming no settlement slippage, which has been clean on both books through 2026.
The caveat: crypto volatility can move this spread faster than you can execute both legs. Scale in and watch for the 8am ET and 4pm ET liquidity windows.
NFL Super Bowl LXI: Divergent Sharp Money
Super Bowl futures are showing a surprising dislocation on the Buffalo Bills to win. Kalshi has them at 14%, Polymarket at 11%. On its own that is noise, but the same 3-cent pattern is holding on Baltimore (12% Kalshi vs 9% Polymarket) and Detroit (16% vs 13%).
This is less a classic arbitrage and more a sharp-money divergence: Polymarket’s NFL book has been consistently tighter on favorites and looser on second-tier contenders since Week 8. For traders willing to build a basket of NO positions on Kalshi’s three overpriced contenders against YES positions on Polymarket’s correspondingly underpriced ones, the expected value edge is meaningful even accounting for correlated outcomes.
Risks and Execution Notes
Arbitrage opportunities between regulated and offshore prediction market venues are real, but they are not risk-free. Capital is locked in both legs until resolution, platform-specific settlement disputes do occur, and withdrawal frictions on Polymarket can delay rebalancing. Position sizing should reflect that these are “lock and wait” trades, not instant arbs.
We also note that convergence often happens fast once a catalyst hits. The Fed spread above has already narrowed by one cent since Thursday. If you are not set up to execute on both venues in parallel, these windows close before you can reach them.
Where to Trade
The two venues referenced throughout this analysis are the deepest-liquidity options for US-eligible traders:
- Kalshi — US-regulated, CFTC-supervised, strongest liquidity on macro and political contracts.
- Polymarket — International crypto-settled book, deepest on crypto and international politics, variable US access.
For a complete platform comparison and current rankings by volume, liquidity depth, and fee structure, see our Best Prediction Markets page.
Analysis reflects market pricing as of November 8, 2026. Prediction market odds move continuously; verify current pricing before executing any position.