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

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. Marshall's chance in our model rose from 60% to 72%.

The expected margin moved in the same direction. Our model's mean outcome is now Marshall by 3.2 points, up from 1.5 points in the earlier run. The model's range of plausible results also shifted toward the Republican. Its 5th-to-95th percentile span now runs from Marshall by 12.4 points to Hamilton by 6.1, compared with Marshall by 11.0 to Hamilton by 8.1 before.

This note does not come with a new Kansas poll we can cite, and nothing in the material behind this update identifies what drove the change. The model moved. The cause is not established here.

The shift partly reverses the movement we reported on September 24, when our Hamilton odds rose to 40%. The current figure is close to where our model stood in mid-September.

Kansas is one input to our national Senate estimate. Our model gives Democrats a 58% chance of winning Senate control and Republicans 41%. Democrats need 51 seats for control and Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to the Republicans. Our model's average outcome is 50.9 Democratic seats, 35 days before the November 3 election.