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Kansas has not elected a Democrat to the U.S. Senate since 1932, and for most of this cycle, Republicans treated Roger Marshall’s seat as noncompetitive. On October 6, the Cook Political Report moved it to Toss Up, with Sabato’s Crystal Ball following on October 14. Kalshi priced Marshall at 82.8% on September 5. As of October 19, Democrat Adam Hamilton trades at 36 cents on Kalshi and 37.5 cents on Polymarket.
Is 37 cents too cheap for a candidate who is tied in the polls? Probably not. Let's dive in.
What the Polling Average Really Shows
First, let’s examine the polling landscape. As of October 10, the RealClearPolitics polling average shows both candidates at 45.8%. Notably, a Wedgewood survey from September 22-24 showed Hamilton at 50% and Marshall at 48%. Including it, the seven public polls since early September give Hamilton a slight edge of about half a point. In a competitive race, this typically results in prices near 50%.
Where the Undecided Vote Breaks in Kansas
A 45.8% to 45.8% tie also leaves about 8% of voters unaccounted for. In Emerson College’s September survey of 750 likely Kansas voters, 8% were undecided, and another 4% backed Libertarian David Graham. In a state Donald Trump carried by 16 points in 2024, late deciders are more likely to lean Republican. Splitting the 8% who were undecided 60-40 for Marshall moves the expected margin 1.5 points toward the incumbent.
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Why Kansas Senate Polls Have Missed Before
Kansas Senate polling also has a record. In 2014, independent Greg Orman led Republican Pat Roberts by 0.8 points in the final RealClearPolitics average, and Roberts won by nearly 11. In 2020, the final New York Times/Siena poll had Marshall up four over Democrat Barbara Bollier, and he won by 11.4.
Governor races in the state haven’t shown the same tilt (Democrat Laura Kelly beat Republican Kris Kobach by 4.5 points in 2018), so the adjustment here is one point rather than a replay of those misses.
Calculating Hamilton’s Fair Value
That math (Hamilton +0.5, minus 1.5, minus one) leaves Marshall ahead by two. With a standard deviation of 6.5 points, wide enough that the 2014 and 2020 Kansas misses fall within two standard deviations, a two-point Marshall edge gives Hamilton a 37.9% win probability. Here's the latest contract movement at Polymarket.
Campaign Spending and Fundraising in the Marshall-Hamilton Race
The campaign factors largely offset. The Senate Leadership Fund is spending $14 million in Kansas, Axios reported on October 12, against $5 million from the Democratic Senate Majority PAC. Hamilton raised $10.6 million in the third quarter across his campaign and joint fundraising committees, his campaign told Politico on October 13, and has endorsements from former Republican Governors Bill Graves and Mike Hayden.
Trump’s 40% approval in the Emerson survey is why the race is competitive to begin with, but the polls already reflect that.
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Is Hamilton Priced Right at 37 Cents?
Hamilton at 36-37.5 cents is priced appropriately against a 37.9% fair value. The tied polls in the headlines skip the step the market has already factored in: allocating undecided voters in a state that leans Republican by double digits.
What moves the fair value is new data. Every point the polling average shifts toward Hamilton adds roughly six points to his fair value. Trump is stumping for Marshall in Wichita on Monday, October 19, and that will be the next test of how many Republican-leaning undecideds come home.
