Kansas Senate Election Winner 2026

What this market asks

Who will win Kansas's 2026 U.S. Senate race? The main options are Democrat Adam Hamilton and Republican incumbent Sen. Roger Marshall. Each price is the market's implied chance that candidate wins.

The bottom line

Polymarket gives Republican Sen. Roger Marshall 63.5% and Democrat Adam Hamilton 36.5%, on about $0.9 million traded. That's down from about 92% for Marshall a year ago. Odds as of 4:00 PM PT, October 15, 2026.

What moved it

Late 2025: barely traded. Marshall sat at about 92% for weeks with almost no price changes, which usually means few trades rather than strong conviction.

January 21: a one-day spike. Marshall dropped from 90% to 63% on January 21 and was back near 84% the next day. We couldn't find news that explains it. On a thinly traded market, swings like this can come from a few large trades.

Spring and summer: slow drift. Marshall eased into the high 70s and low 80s from February through mid-September. We didn't find a single event behind it.

Late September to October: the big slide. Marshall fell from about 74% on September 21 to about 62% by October 8. Polls in that window mostly showed Hamilton tied or narrowly ahead: Trafalgar (Sept. 29–Oct. 1) had Hamilton 44.4% to 43.5%, and YouGov (Sept. 24–Oct. 4) had Hamilton 48% to 45% (Newsweek, Oct. 14). On October 6 Marshall dipped from 68% to 64%. Hamilton's pollster GBAO released a memo that day showing him up 5 and saying Cook Political Report had moved the race to Toss Up "just today" (GBAO memo, Oct. 6; partisan source).

How it settles

Polymarket resolves this market once the Associated Press, Fox News and NBC have all called the race for the same candidate. If they don't all agree, it waits for the official state certification. Polymarket's own market page has the full rules.

Who's calling it

See 2 forecaster calls on X for this race, with links to each post →

• Sabato's Crystal Ball moved Kansas from Leans Republican to Toss-Up on October 14 (Newsweek).
• Cook Political Report also rates it a Toss-Up (same source).
• Recent polls: InsiderAdvantage (Oct. 9–10) has Hamilton 47.5% to 46.7% (same source).

The contrarian take

The market still makes Marshall a clear favorite at 63.5%, while the two ratings above call it a pure toss-up and recent public polls show Hamilton level or slightly ahead. For the polls to be right, Hamilton would need to win in a state that hasn't elected a Democratic senator since 1932 (same source). The market is betting Kansas's partisan lean beats the polling.

What to watch

• New polls, especially nonpartisan ones, after the Toss-Up ratings.
• Republican outside spending. Sabato pointed to Senate Leadership Fund money as a sign of a "rescue operation."
• Election Day, November 3.

This is a plain-English summary of Polymarket's resolution rules. Polymarket's own market page has the full, official rules.