On September 8 the New York Times reported that Roger Marshall and the OB-GYN practice he owned in Great Bend had sued more than 700 of his former patients over unpaid bills, and that more than 80 of them were arrested after missing court dates. The night before, Kalshi's last trade had the Kansas senator at 84¢ to win re-election. He closed September 8 at 80¢, two cents below that day's open and four below the previous session's last trade. He heard a State Fair crowd chant "shame on you" as he defended the suits four days later, and the rest of the move came in the sessions after that: as of this update he sits at 77¢ to buy. Adam Hamilton, the Democrat, is 25¢, up from 18¢ when this page first published on September 5. Seven cents matches the whole August climb, and for the first time in the race it came on a news story rather than a poll.
That is the thing worth knowing about this market now. Kalshi traders piled into Hamilton in one burst on September 4 and the price went nowhere for three days. A second burst on Labor Day did the same. Since the August primary the price had absorbed two Democratic-aligned polls, a wave of attack ads and three rating houses moving to Likely Republican, and had answered all of it with a slow drift back to 18¢. Then a newspaper did in one session what none of that had done, and a debate crowd finished the job. The rest of this page is about whether the new price has earned a poll to back it, because the only survey taken during the move says it has not.
What a smaller Marshall win looks like is priced on its own board, further down, and it has moved more than the winner market has.
The Board Right Now
Two contracts, one per party, and both have moved seven cents since this page first published.
| Contract | Cost to buy (ask) | Bid | Last trade | Sept. 5 cost to buy |
|---|---|---|---|---|
| Roger Marshall (R) Wins | 77¢ | 76¢ | 76¢ | 84¢ |
| Adam Hamilton (D) Wins | 25¢ | 24¢ | 25¢ | 18¢ |
Prices are from the Kalshi trade API as of September 16, 2026, at 4:45 a.m. ET. The cost to buy is what a new buyer pays right now; the bid is what a seller gets. The last column is what the same contracts cost when this page first published.
The row to sit with is the second one. At 25¢ the market gives Adam Hamilton one chance in four of becoming the first Democrat Kansas has sent to the Senate since 1932, up from a little better than one in six eleven days ago. That is the same size of move as the whole August climb, which took twelve days, a one-point poll and the primary itself to reach 23¢. This one took eight sessions and no poll in Hamilton's favor to pass it.
What Moved Since The Lawsuits Report
Since this page's last update on September 13, Hamilton has gone from a 22¢ close that Sunday to 25¢ on Tuesday, September 15, his highest close in our window, and Marshall from 79¢ to 76¢, his lowest. Those three sessions are the tail of a move that began on September 8, so the table starts the session before it.
| Session (ET) | Hamilton (D) close | Marshall (R) close | What happened |
|---|---|---|---|
| Sept. 7 | 18¢ | 84¢ | Labor Day; a second burst of Hamilton buying, and the price still closed where the September 4 burst left it |
| Sept. 8 | 20¢ | 80¢ | New York Times reports the patient lawsuits; Hamilton prints as high as 22¢, Marshall as low as 78¢ |
| Sept. 10 | 21¢ | 80¢ | Hamilton prints as high as 23¢; co/efficient's poll finishes fielding |
| Sept. 12 | 20¢ | 79¢ | State Fair debate, 1:30 p.m.; the price barely moves on the day |
| Sept. 13 | 22¢ | 79¢ | Post-debate coverage; Hamilton's first close above 21¢ in September |
| Sept. 15 | 25¢ | 76¢ | Hamilton's highest close and Marshall's lowest since our daily prices begin in late July |
The row that carries the move is September 8. The Times analysis of Kansas court records, as KCUR summarized it that morning, found that Marshall and his practice sued more than 700 former patients over medical debt across a career that ended when he went to Congress in 2016, that more than 80 were arrested after missing court dates, and that some had wages garnished. Newsweek's account adds that the bills ran from $101 to several thousand dollars and carried 18% annual interest, and that 81 patients were arrested. Hamilton's contract opened that session at 16¢ and closed at 20¢, the first session in our September record where a news story, not a poll, moved this price more than a cent. Marshall's campaign answered, as KCTV5 reported on September 10: "Sixty days before an election, the New York Times has decided that a rural doctor keeping the hospital's lights on is some kind of scandal." Hamilton's statement in the same story: "Roger Marshall must explain to Kansans why he had patients arrested and jailed over tiny debts before going to Congress to vote to take away Kansans' health coverage."
The climb paused on its own at the September 9 close, and when the poll fielded in the middle of the move was reported on September 11 it argued the pause was right. co/efficient's September 8-10 survey of 915 likely voters, from a Kansas City firm that the Sunflower State Journal notes mostly works for Republicans, had Marshall 49%, Hamilton 44%, Libertarian David Graham 2% and 5% undecided. A five-point lead is the best number the incumbent has had since the primary, and the market held its range for four sessions around it: Hamilton closed 20¢, 21¢, 21¢ and 20¢ from Wednesday through debate day.
Then the debate did what the poll could not. Marshall and Hamilton met at 1:30 p.m. on Saturday, September 12, at the State Fair in Hutchinson, on 580 WIBW, in front of bleachers that the Kansas Reflector's Anna Kaminski described as booing and heckling the incumbent's answers while Hamilton went after him on tariffs, inaction on the war in Iran, health care and food-assistance cuts. When the Reflector's Tim Carpenter put the Times reporting to him, Marshall called it "a political hit job" and said one in five of his patients had received free care, per Ad Astra Radio's recap, and the crowd broke into a chant of "shame on you" as he defended the suits, Newsweek reported. He told the crowd "My opponent is too woke, he's too weak and he doesn't stand for anything." Hamilton called the administration's decision to import beef from Mexico "a slap in the face" to Kansas cattle producers. Hamilton's contract closed 22¢ the next two sessions and 25¢ on Tuesday.
What did not move is the ratings consensus. The race's ratings table lists Cook Political Report, Decision Desk HQ, FiftyPlusOne, Fox News, Inside Elections, Sabato's Crystal Ball, Silver Bulletin and Split Ticket at Likely Republican, The Economist and RealClearPolitics at Lean Republican and Race to the WH at Tilt Republican; the table's Cook entry carries a September 15 date, a week after the report, still at Likely Republican. The market has moved from the Likely end of that range toward the Lean end on a story and a debate, and that is the tension the rest of this page prices: a one-in-four Democrat in a state Trump carried by 16 points, on a record the forecasters have read and the price has finally traded.
The Market At A Glance
The contract terms, for anyone checking what a price here actually pays on.
| Venue | Kalshi |
| The Event | The November 3, 2026 general election for Kansas's U.S. Senate seat: incumbent Republican Sen. Roger Marshall against Democrat Adam Hamilton, with Libertarian David Graham also on the ballot |
| How It Settles | Each contract is priced by party. The Republican contract pays $1 "if a representative of the Republican party is sworn in as a Senator of Kansas for the term beginning in 2027," and the Democratic contract reads the same way for Democrats. Because both are party contracts, a David Graham win would settle both to No. The two asks add to 102¢ because a buyer crosses a one-cent spread on each side; the two bids add to exactly 100 |
| What A Cent Means | 25¢ to buy Hamilton means $100 becomes $400 if he wins and $0 if he does not, before Kalshi's trading fee |
| Snapshot | Prices at 4:45 a.m. ET, Wednesday, September 16, 2026; session closes are the last trade of each Eastern calendar day, from the Kalshi trade log |
The prices and probabilities on this page are market prices and model estimates, not predictions of fact and not financial advice. This article does not advocate for or against any candidate or party.
What The Polls Say
Until September every general-election poll of this race had come from a Democratic-aligned pollster, which is the first thing to know before reading the numbers. The co/efficient survey is the first from a Republican-aligned firm, and it is the best number Marshall has had since the primary.
| Pollster | Field dates | Sample | Marshall | Hamilton |
|---|---|---|---|---|
| co/efficient (R-leaning firm, no sponsor listed) | Sept. 8-10 | 915 LV | 49% | 44% |
| Global Strategy Group (D) | Aug. 12-16 | 800 LV | 43% | 44% |
| Public Policy Polling (D) | Aug. 7-8 | 569 | 46% | 45% |
| GBAO (D), Listed Elsewhere As GQR | July 8-13 | 600 LV | 47% | 43% |
| Tavern Research (D) | Jan. 28 | 1,013 LV | 54% | 46% |
The first row is the one that argues with the price. Marshall's favorability in that survey, as Newsweek reported it, was 42% favorable to 44% unfavorable, with Hamilton at 34% to 27% and 39% of voters holding no opinion of him, which is the profile of a challenger most of the state has not met yet. The third row is the one the August move tracked. Public Policy Polling's survey for Senate Majority PAC, reported by the Sunflower State Journal on August 12, had Marshall 46% to Hamilton 45% with 9% undecided, and Hamilton's contract closed at 22¢ that day. A Global Strategy Group poll fielded August 12 through 16 had Hamilton a point ahead outright, and the market did not follow: the Democrat's high close was 23¢ on August 16, he drifted back to 18¢ over the following two weeks, and it took a September news story, not that poll, to carry him past 23¢.
The forecasters moved once, in the days after the primary, and their entries have not changed since. Back then, Cook Political Report and Sabato's Crystal Ball both shifted Kansas from Safe or Solid Republican to Likely Republican, and Fox News made the same move on August 18. Sabato's Kyle Kondik put the case for caution in one sentence: "So this is definitely a long shot, although Hamilton out-raised incumbent Sen. Roger Marshall (R-KS) $3.7 million to $610,000 last quarter." Cumulatively Marshall still has the bank, $4.78 million cash on hand through June 30 to Hamilton's $2.60 million in FEC filings, so the out-raise is a quarter, not a position. At 25¢ the market still agrees with the word "long shot" while pricing the shot shorter than the ratings do, and shorter than a 49-44 poll implies.
Where The Price Has Been Since The Primary
Session closes since primary night, with the event that sat behind each one.
| Date (Session Close, ET) | Hamilton (D) | Marshall (R) | What happened |
|---|---|---|---|
| Aug. 4 | 16¢ | 85¢ | Primary day: Marshall took 79.9% of the Republican primary, Hamilton 34.8% of the Democratic primary |
| Aug. 8 | 20¢ | 81¢ | Post-primary drift; Cook and Sabato shifts to Likely R reported by Aug. 9 |
| Aug. 12 | 22¢ | 78¢ | PPP poll reported: Marshall 46, Hamilton 45 |
| Aug. 16 | 23¢ | 79¢ | Hamilton's August high; GSG poll fielding |
| Aug. 21 | 20¢ | 84¢ | Marshall a cent under his 85¢ primary-day close |
| Aug. 28 | 18¢ | 83¢ | The drift settles |
| Sept. 4 | 18¢ | 83¢ | A burst of Hamilton buying that the price absorbed without moving |
| Sept. 8 | 20¢ | 80¢ | New York Times patient-lawsuits report; Hamilton prints 22¢ |
| Sept. 10 | 21¢ | 80¢ | Hamilton prints 23¢; co/efficient poll fielding ends |
| Sept. 12 | 20¢ | 79¢ | State Fair debate |
| Sept. 15 | 25¢ | 76¢ | Hamilton's highest close, Marshall's lowest, in our window |
More live boards: the full 2026 Senate board, where Kansas sat at 79.5¢ against an 82% panel read at its September 11 refresh · the 2026 Senate control board, a Republican Senate 46¢ to buy on Kalshi as of this update · every open board on the prediction markets hub.
Read the table top to bottom and the shape is a hill with a second, taller hill after it. Hamilton climbed seven cents in the twelve days after the primary, peaked at 23¢ on August 16, gave five of them back over the next twelve days, and never closed outside 17¢ to 18¢ from September 1 through Labor Day. Marshall's contract was the mirror: down seven cents to 78¢ by August 12, back to 84¢ by August 21, and between 81¢ and 84¢ through Labor Day. Kalshi's own politics account posted the race at Marshall 80%, Hamilton 20% on August 12, within a couple of cents of that week's closes. The two bursts of Hamilton buying on September 4 and September 7 landed on a price pinned at 18¢ and could not move it, which is the part I keep coming back to: there was a seller willing to hand out the Democrat at 18¢ in any size that week, and by the following Thursday there was not. The second hill started September 8 and has not yet shown a top.
The Record Both Campaigns Are Running On
Eight documented items now sit behind the ad war. Five of them were public before Hamilton's contract ever got past 23¢, two more landed inside our price window and moved it a cent or less, and the eighth moved it four cents in a day. Both campaigns were already on the air against each other before the report, KWCH reported on August 19, Hamilton's spots saying "Marshall votes for tariffs and war" and Marshall-side spots calling the pastor "Way too woke for Kansas." Here is the record on both sides, with sources, and next to each item what the price did.
Marshall, four items. The newest is the one that moved the price. On September 8 the New York Times, analyzing Kansas court records, reported that Marshall and the OB-GYN practice he owned filed debt-collection suits against more than 700 former patients, that more than 80 of them (81, by Newsweek's count) were arrested after missing court dates, and that some had wages garnished, per KCUR's same-day summary and Newsweek. KCUR noted that Marshall introduced a bill in 2025 that would bar hospitals from suing patients unless they post their prices publicly. His campaign's Payton Fuller told Newsweek the practice "provided millions in uncompensated care" and "used the exact same billing and outside collection procedures as every other business or hospital in Kansas." Hamilton's contract went from 16¢ to 20¢ that session, and the report was put to Marshall directly at the September 12 debate. In March 2025 he left a Saturday town hall in Oakley about 45 minutes into a scheduled hour after telling the crowd "if you keep interrupting me, I'm going to leave," KAKE reported; his office said "Democrat operatives who couldn't place Oakley, Kansas on a map before today sabotaged a local town hall — even still, Senator Marshall stayed and answered every question that was asked for 45 minutes." That predates this market's run entirely. In June, after Hamilton raised a 2025 Kansas law under which a Senate vacancy after May 1 and before October 2 of an election year lets an appointed replacement skip the election for two years, Marshall answered on the record, per KMUW: "I am ruling out any appointment in the Trump administration at least through the next two or two or three years." And on August 31, during a telephone town hall, he said he was "frustrated" by President Trump's beef imports but called them necessary, KCUR reported; the Hamilton contract closed unchanged at 19¢ that session, and at the debate Marshall told the crowd "This is not the first time I've disagreed with President Trump, and it probably won't be."
Hamilton, four items. In April the Kansas GOP's executive director filed a Federal Election Commission complaint alleging Hamilton "blatantly used the corporate resources of the church" to promote his February exploratory video, KMUW reported; the church called the video the "regular way significant information is shared with our congregation," and no FEC action has been reported. In July, Kansas Reflector reporting carried by HPPR found former church employees split on his leadership and revisited a 2005 report that a church volunteer had touched boys at a church camp, which the church handled with an internal inquiry that proved inconclusive; when a second accusation came in 2006 the church reported it to authorities immediately, the volunteer pleaded guilty to misdemeanor sexual battery in 2013 and died in 2015, and Hamilton now says he "would have handled the 2005 incident differently by going directly to law enforcement." Both of those predate our price window. In August a Main Street Fund ad called him a "woke megachurch CEO," and HuffPost's fact-check found no evidence for its claim that church funds paid for "drag queen story time for kids" and reported the ad spliced a sermon line from words about 200 words apart; the Hamilton contract closed at 22¢ on August 15. And Sen. Ted Cruz called a 2022 Hamilton sermon on non-Christians and heaven "heretical," to which the campaign told the Christian Post on August 17 that "Adam was not speaking of universalism" but "was discussing inclusivism"; that session also closed at 22¢.
Now price it. Only one of the three earlier Marshall items, the August 31 beef-imports town hall, falls inside our price window, and it did not move the Hamilton contract at all; the other two predate the daily prices entirely. Of the Hamilton items, only the August 17 Cruz comment landed inside the window, and the contract closed a cent lower that day. The other five of the original seven were public before August 16, the day Hamilton's contract first peaked at 23¢, and the market's answer to that record was a seven-cent rise followed by a five-cent retreat. The eighth item broke the pattern: the September 8 report is the first entry in this record that moved the price on the day it landed, four cents in one session, and the debate that put it to Marshall in front of a live crowd is what carried the price past the August high. The market that had looked like a fundamentals question, a Republican state against a well-funded challenger, has now shown it will trade a revelation when the revelation is about the incumbent. Hamilton's own framing on primary night, as KWCH quoted it, was that "Tonight Kansans said they had enough of the chaos and corruption in Roger Marshall's Washington DC." The price puts roughly one chance in four on that reading and three in four against it.
The Margin Ladder: A Marshall Win Smaller Than 2020
Kalshi also runs a side market on how big a Republican win would be, and it says something the winner market cannot. Think of it as the market betting on Marshall's margin rather than his name.
| Republicans Win By | Cost to buy | Bid | Last trade | Sept. 5 cost to buy |
|---|---|---|---|---|
| 3 Points Or More | 67¢ | 59¢ | 59¢ | 82¢ |
| 5 Or More | 58¢ | 49¢ | 59¢ | 70¢ |
| 7 Or More | 37¢ | 31¢ | 32¢ | 48¢ |
| 9 Or More | 33¢ | 32¢ | 34¢ | 35¢ |
| 11 Or More | 16¢ | 12¢ | 17¢ | 24¢ |
| 13 Or More | 13¢ | 3¢ | 11¢ | 17¢ |
| 15 Or More | 9¢ | 4¢ | 13¢ | 13¢ |
This is the board the opening promised, and it has moved more than the winner market. Start at "11 or more," last traded at 17¢, and a buyer today pays 16¢ to get on. Marshall won this seat in 2020 by 11.43 points, 53.22% to 41.79% over Barbara Bollier. The ladder prices a repeat of that margin at about one chance in six, down from one in four on September 5, while a win of any size sits at 77¢ on the main board. Read together, the two markets say the same thing from two angles: Marshall is still the favorite to win, and the ladder's buyers expect him to win by a good deal less than he did last time. Every rung's ask has come down since September 5, and with the caution below in mind, since only one rung has traded in the last day, the sizes are still telling. "3 or more" cost 82¢ then and 67¢ now, a fifteen-cent drop against seven on the winner contract; "7 or more" has gone from a near coin flip at 48¢ to 37¢; and "9 or more" at 33¢ says two chances in three that the margin stays under nine. Rungs run on up to 23 points, and the ones above 15 have barely traded.
One caution the table cannot show. These rungs are thin: the gap between bid and ask runs six to nine cents on three of the top four rows, and only the "9 or more" rung traded at all in the 24 hours before this update. A single mid-sized order would move any row here, where the winner market absorbed two bursts of buying in four days without moving. Treat the ladder as a considered opinion from a small room, not as a price you could trade in size.
What Moves This Next
The first scheduled test came at the State Fair, and the price moved against the incumbent: Hamilton closed 20¢ on debate day and 25¢ three sessions later. No second debate is on the public calendar; Libertarian David Graham was excluded from the first. The next fixed date is October 15, when third-quarter fundraising reports are due at the FEC and the market learns whether Hamilton's $3.7 million second quarter was a surge or a level. Between now and then the test is simpler: whether a poll from a firm with no partisan client book confirms the 49-44 co/efficient number or the one-in-four price. As of this update the price is the one making the bolder claim.
The second thing to watch is whether the September 4 pattern repeats, because it already has once. On the morning of Thursday, September 10, the same two-sided trade that had failed to move the price on September 4 was placed again, Marshall sold at 79¢ and Hamilton bought seconds later at 20¢ to 22¢, and this time the price moved: the session opened at 19¢, printed 23¢ and closed at 21¢. The resting seller who handed out the Democrat at 18¢ in any size on September 4 was not there at 21¢ six days later, and that absence is the clearest sign on this page that the lawsuits report changed what Kansas is worth to the people who trade it. If you are new to how a Kalshi contract, its one-cent spread and its trading fee turn a price into a chance, the Kalshi explainer and the fee guide cover the mechanics so this page does not have to.
The last date is the one the contract actually settles on: the winner is sworn in for the term beginning in 2027, and a race called on the night of November 3 is not yet a settled contract. For how this seat fits the national count, the 2026 Senate control board prices a Republican Senate at 46¢ to buy, and the balance-of-power board prices every chamber path in one place. The gap this page keeps circling, a five-point poll lead for the incumbent against a price that has drifted to one chance in four for the challenger, is the kind of mismatch between a number and a narrative that our sports tools are built to find. The Kansas race is not carried on OddsShopper, but if you want to watch that method run on this week's games, our free expert picks are the place to start.
In Summary
The price in Kansas thought it had finished its argument in mid-August. Hamilton went from 16¢ to 23¢ on a primary win and a one-point poll, gave most of it back, and held at 18¢ through two bursts of buying that could not move it. Then a newspaper did. The September 8 report on the patients Marshall's practice sued took Hamilton to 20¢, a five-point Republican-aligned poll held him there, and the State Fair debate carried him to 25¢, one chance in four, further than the Likely Republican most of the forecast table still reads. The margin ladder's buyers expect a smaller Marshall win than 2020 by more than they did eleven days ago. The line that would change this page next is a poll from a firm with no partisan client book, and until one lands, the price is out ahead of everything else on the record.
Every price cited here is publicly graded once the markets settle, on our prediction market scoreboard, and the rest of the 2026 map is on our every-board Senate tracker.
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