Minnesota Senate forecast drops 28 points in four days as two close polls arrive

Our model has moved 28.3 points toward the Republican in Minnesota's open Senate race over four days. The September 29 run gave the Democrat a 92% chance of winning. The October 3 run gives the Democrat a 63 in 100 chance, and the Republican 37%.

The expected margin moved with it. Our model's mean margin fell from D+7.7 to D+1.8. Its 5th-to-95th percentile range shifted from R+1.5 to D+17.0 in the earlier run to R+7.3 to D+10.9 now. In the earlier run, the Republican end of that range was a narrow loss for the Democrat. It now extends to a Republican margin of more than 7 points.

Two polls entered our data in that span. An InsiderAdvantage survey of 1,200 likely voters, fielded September 28-29, had the Democrat at 46% and the Republican at 45%. A Big Data Poll survey of 622 likely voters, sponsored by the Public Polling Project and fielded September 29-30, had the Democrat at 45.8% and the Republican at 43.6%. Both show a close race. Neither margin is large enough to call a lead.

Both polls arrived between the two runs, and both point to a tighter contest than our earlier estimate. The payload does not break down how much of the 28.3-point shift each poll accounts for, or whether other inputs also changed. This note leaves that split open.

The race bears on the chamber. Our model gives Democrats a 55% chance of Senate control, with a mean of 50.7 Democratic seats against the 51 they need. Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to them.