Marist puts Turek up eight in Iowa, and our estimate crosses to 56 in 100

A Marist University survey of 1,050 registered voters in Iowa, fielded September 17-20, has Democrat Josh Turek at 50 percent and Republican Ashley Hinson at 42 percent. That is the widest margin in the polling our model has seen in this race in recent weeks, and it arrived after a run of surveys that this site covered as close or narrowly split.

Our model now gives Turek a 56 in 100 chance of winning the seat, with a mean margin of D+0.8 and a 5th-to-95th percentile range running from R+8.8 to D+10.4. The run before this one, at 4:32 AM ET on September 22, put Turek's chance at 41 percent with a mean margin of R+1.3. So this is a change, not a confirmation: a single survey moved our estimate roughly 15 points and shifted the central margin from a narrow Republican edge to a narrow Democratic one.

The width of that range is the more important number. Even at 56 percent, our model still treats the race as close to a coin flip, and the interval spans nearly nine points of Republican margin on one side and better than ten points of Democratic margin on the other. One poll carrying that much weight is a sign of how thin the evidence is, not how settled it is.

The seat is open; Joni Ernst is the Republican incumbent. Iowa matters to the chamber arithmetic. Our model puts the Democratic mean at 50.6 Senate seats, with 51 needed for Democratic control and 50 enough for Republican control, because the vice president is a Republican and a 50-50 tie goes to the Republicans. Democrats have a 54 percent chance of winning Senate control in our current run, against 45 percent for Republicans.