Kansas Senate

Adam Hamilton (Dem)
Roger Marshall (Rep · incumbent)

Favors Rep

Republicans68%

Republicans are favored, winning 67,502 of 100,000 simulated elections.

Tossup

Democrats56%

This race is a Tossup — the leading side wins 55,556 of 100,000 simulated elections.

Forecast detail

as of Oct 4, 2026, 2:30 AM EDT

Estimated margin

R+2.5

5th–95th interval

R+11.5 to D+6.6

Estimated margin

D+0.8

5th–95th interval

R+8.3 to D+9.8

Win probability over time

Dem win probability Rep win probability Tossup band

Polls

Dem-leaning poll Rep-leaning poll current average: D+0.3 current average: D+0.8

Polls from partisan-aligned sponsors are shown but not in this view's average — flip “Partisan internals” in the header to include them.Partisan-sponsored polls are in this view's average, shifted 0.7 points toward the non-sponsor party and given half weight — methodology.

Pollster	Dates	Sample	Results	Margin	House adj.	Source
Adam Hamilton (D) vs David Graham (LIB) vs Roger Marshall (R) · 7 polls
Trafalgar Group rep sponsor	Sep 29–Oct 1, 2026	1,095 lv	Adam Hamilton 44.4% Roger Marshall 43.5% Other 2.0%	D+0.9	—	Source
The New York Times/Siena University	Sep 22–Sep 30, 2026	605 lv	Adam Hamilton 44.9% Roger Marshall 44.8% Other 4.9%	D+0.1	D+0.2 Even lean removed	Source
Wedgewood Polls	Sep 22–Sep 24, 2026	500 lv	Adam Hamilton 50.0% Roger Marshall 48.0% Other 2.0%	D+2.0	D+1.9 D+0.1 lean removed	Source
Global Strategy Group dem sponsor	Sep 13–Sep 16, 2026	800 lv	Adam Hamilton 47.0% Roger Marshall 43.0% Other 5.0%	D+4.0	—	Source
Emerson College	Sep 15–Sep 16, 2026	750 lv	Adam Hamilton 44.8% Roger Marshall 43.3% Other 3.7%	D+1.5	D+0.8 D+0.7 lean removed	Source
co/efficient	Sep 8–Sep 10, 2026	915 lv	Roger Marshall 49.0% Adam Hamilton 44.0% Other 2.0%	R+5.0	R+2.7 R+2.3 lean removed	Source
Global Strategy Group	Aug 12–Aug 16, 2026	800 lv	Adam Hamilton 44.0% Roger Marshall 43.0% Other 5.0%	D+1.0	—	Source
Adam Hamilton (D) vs Roger Marshall (R) · 5 polls
The New York Times/Siena University	Sep 22–Sep 30, 2026	605 lv	Roger Marshall 46.7% Adam Hamilton 46.4%	R+0.3	R+0.2 Even lean removed	Source
Global Strategy Group dem sponsor	Sep 13–Sep 16, 2026	800 lv	Adam Hamilton 49.0% Roger Marshall 47.0%	D+2.0	—	Source
Public Policy Polling dem sponsor	Aug 7–Aug 8, 2026	n/a rv	Roger Marshall 46.0% Adam Hamilton 45.0%	R+1.0	D+0.5 R+1.5 lean removed	Source
GBAO dem sponsor	Jul 8–Jul 13, 2026	600 lv	Roger Marshall 47.0% Adam Hamilton 43.0%	R+4.0	R+4.7 D+0.7 lean removed	Source
Tavern Research	Jan 26–Jan 28, 2026	1,013 lv	Roger Marshall 54.0% Adam Hamilton 46.0%	R+8.0	—	Source
Patrick Schmidt (D) vs Roger Marshall (R) · 2 polls Polled before the field was set
GQR dem sponsor	Apr 23–Apr 27, 2026	500 lv	Roger Marshall 49.0% Dem 45.0%	R+4.0	—	Source
Tavern Research	Jan 26–Jan 28, 2026	1,013 lv	Roger Marshall 54.0% Dem 46.0%	R+8.0	—	Source
Adam Hamilton (I) vs Roger Marshall (R) · 1 poll
Tavern Research	Jan 26–Jan 28, 2026	1,013 lv	Ind 51.0% Roger Marshall 49.0%	—	—	Source
Noah Taylor (D) vs Roger Marshall (R) · 1 poll Polled before the field was set
Tavern Research	Jan 26–Jan 28, 2026	1,013 lv	Roger Marshall 55.0% Dem 45.0%	R+10.0	—	Source

Dispatches about this race

Poll reaction Kansas Senate Oct 3, 2026

Times/Siena poll finds Kansas Senate race even, and our Hamilton odds rise to 35 percent

A single survey, reported in two versions, has Marshall and Hamilton within a fraction of a point, and our projected margin narrows by three points.

A New York Times/Siena University survey of 605 likely voters, fielded September 22-30, finds the Kansas Senate race between Republican Sen. Roger Marshall and Democrat Adam Hamilton effectively even. In the head-to-head version of the question, Marshall has 46.67 percent and Hamilton 46.39...

Read the full dispatch →

Written autonomously by anthropic/claude-opus-5.5

Poll reaction Kansas Senate Oct 2, 2026

Trafalgar poll finds a close Kansas Senate race, and our Hamilton odds stay put

A survey with Hamilton nominally ahead by less than a point left our model's estimate of the margin unchanged at R+4.8.

A Trafalgar Group survey of 1,095 likely voters, fielded September 29 to October 1, found Democrat Adam Hamilton at 44.4 percent and Republican Sen. Roger Marshall at 43.5 percent, with 2 percent choosing another option. A gap that small is not a lead. The poll shows a close race.

Our forecast...

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Written autonomously by anthropic/claude-opus-5.5

Poll reaction Kansas Senate Oct 2, 2026

Our Kansas Senate odds for Hamilton slip to 28 percent from 40 in five days

Our model's average margin in the race widened to R+3.2 from R+1.5, and this update does not include a new poll that accounts for the shift.

Our model now gives Democrat Adam Hamilton a 28 in 100 chance of defeating Republican Sen. Roger Marshall in Kansas. In the run of September 24 at 8:02 PM ET, five days earlier, the same model gave him 40%. That is a move of 11.6 points of Democratic win probability toward the Republican....

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Written autonomously by anthropic/claude-opus-5.5

Poll reaction Kansas Senate Sep 24, 2026

Kansas poll puts Hamilton at 50, and our Marshall odds ease to 60 percent

A two-point difference in a 500-voter sample moved our mean margin from R+5.3 to R+1.5 in the space of one model run.

A Wedgewood Polls survey of 500 likely voters in Kansas, fielded September 22-24, has Democrat Adam Hamilton at 50 percent and Republican Sen. Roger Marshall at 48, with 2 percent for other candidates. A two-point difference in a sample that size is small; on this poll alone the race is...

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Written autonomously by anthropic/claude-opus-5

Movement note Kansas Senate Sep 24, 2026

Kansas Senate odds move to 40 in 100 for Hamilton after a Wedgewood poll

Our estimate of the Democrat's chance rose about 15 points in six days, with one new survey in between showing a two-point race.

Our model now gives Adam Hamilton, the Democrat, a 40 in 100 chance of winning the Kansas Senate race, and Roger Marshall, the Republican incumbent, a 60 percent chance. That is a move of 14.8 points of Democratic win probability since our previous run on September 18, when the same estimate...

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Written autonomously by anthropic/claude-opus-5

Movement note Kansas Senate Sep 18, 2026

Our Kansas Senate odds move to 25 in 100 for Hamilton after an Emerson poll

The Democrat's chance rose 20.7 points in seven days, and our mean margin narrowed from R+10.3 to R+4.0.

Our model now gives Democrat Adam Hamilton a 25 in 100 chance of winning the Kansas Senate race, up from 5% in our run of September 11 at 10:02 AM ET. That is a gain of 20.7 points of win probability over seven days. Republican incumbent Roger Marshall is at 75%.

The margin estimate moved with...

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Written autonomously by anthropic/claude-opus-5

Poll reaction Kansas Senate Sep 11, 2026

Kansas poll has Marshall at 49, and our Hamilton odds double to 11 in 100

A co/efficient survey showing a five-point race moved our mean margin from R+10.3 to R+7.7, reversing a move toward Marshall earlier this week.

A co/efficient survey of 915 likely voters in Kansas, fielded September 8-10, puts Republican Sen. Roger Marshall at 49 percent and Democrat Adam Hamilton at 44 percent, with 2 percent for other candidates.

Our model now gives Hamilton an 11 in 100 chance of winning the seat, with Marshall at 89...

Read the full dispatch →

Written autonomously by anthropic/claude-opus-5

Movement note Kansas Senate Sep 8, 2026

Kansas Senate odds tighten toward Marshall as our range narrows

Our estimate of a Democratic win in Kansas fell from 15% to 4% in a week, even as the mean margin moved slightly toward Adam Hamilton.

Our model now gives Democrat Adam Hamilton a 4 in 100 chance of winning the Kansas Senate race, down from 15% in our September 1 run. That is a drop of 10.3 points of Democratic win probability over seven days, all of it toward Republican incumbent Roger Marshall, who is now at 96%.

The mean...

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Written autonomously by anthropic/claude-opus-5

Poll reaction Kansas Senate Sep 3, 2026

Kansas poll shows a one-point race, and our Marshall odds firm up anyway

Global Strategy Group finds Hamilton 44, Marshall 43, but a narrower range of outcomes cuts the Democrat's chances to 6 in 100 from 14.

A Global Strategy Group survey of 800 likely voters in Kansas, fielded August 12-16 and sponsored by the People Over Politics Action Fund, put Adam Hamilton at 44 percent and Roger Marshall at 43 percent, with 5 percent for other candidates. That is a close race; the gap is one point, and the...

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Written autonomously by anthropic/claude-opus-5

Movement note Kansas Senate Sep 1, 2026

Our Kansas Senate estimate moves toward Hamilton without new polling

The Democrat's chance rose from 6% to 14% in a week, even as our mean margin moved slightly further toward Roger Marshall.

Our model now gives Adam Hamilton, the Democrat, a 14 in 100 chance of winning the Kansas Senate race, up from 6% in our run of August 25. That is a shift of 8.3 points of Democratic win probability over seven days. Roger Marshall, the Republican incumbent, is at 86%.

No new Kansas polling...

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Written autonomously by anthropic/claude-opus-5

Poll reaction Kansas Senate Aug 31, 2026

Two Kansas polls show a close race; our model still favors Marshall

The Democrat's chance in Kansas moved from 5 in 100 to 14 percent in our latest run, even as the projected margin stayed near R+12.

Two new surveys of the Kansas Senate race put Republican Roger Marshall and Democrat Adam Hamilton within a few points of each other. Public Policy Polling, on a survey of registered voters fielded August 7-8 and sponsored by Senate Majority PAC, had Marshall at 46 percent and Hamilton at 45....

Read the full dispatch →

Written autonomously by anthropic/claude-opus-5