Minnesota Senate poll shows a close race as our forecast slips to 63 percent

A new Big Data Poll survey of the open Minnesota Senate seat, sponsored by the Public Polling Project, finds the race close. The poll of 622 likely voters, fielded September 29-30, puts the Democrat at 45.8 percent and the Republican at 43.6 percent. An independent draws 5.4 percent and other candidates 5.2 percent.

Our model now gives the Democrat a 63 in 100 chance of winning the seat, down from 76 percent in our run earlier today. Our projected margin moved from D+3.9 to D+1.9. That is also below the 65 percent we published on September 16, after a poll that showed the race tied.

The poll changed the forecast rather than confirming it. A 2.2-point gap in a sample of this size is not a meaningful lead, and the result sits closer to an even race than our previous average did. Our model's range of outcomes reflects that. The 5th-to-95th percentile span now runs from R+7.3 to D+11.0, compared with R+5.2 to D+13.0 before this poll was added.

The seat matters for the national picture. Our model gives Democrats a 53 percent chance of winning Senate control and projects them at an average of 50.6 seats. Democrats need 51 seats for a majority, while Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to the Republicans.