YouGov poll has Iowa Senate race tied, and our estimate moves toward Turek

A YouGov survey of 2,166 registered voters in Iowa, fielded September 3-8, put Democrat Josh Turek at 44 percent and Republican Ashley Hinson at 43 percent. That one-point gap is not a lead in any meaningful sense; the poll describes a close race for the open seat held by Republican Joni Ernst.

Our forecast moved on it. As of 12:02 PM ET, our model gives Turek a 45 in 100 chance and Hinson 55 percent, with a mean margin of R+0.8 and a 5th-to-95th percentile range running from R+10.8 to D+9.3. The run completed at 10:32 AM ET had Turek at 31 percent, Hinson at 69 percent and a mean margin of R+3.1. So this is a change, not a confirmation: the new poll pulled our central estimate more than two points toward the Democrat and cut the gap in the win probabilities from 38 points to 10.

The wide percentile range is the more durable point. Our model still allows outcomes from a comfortable Hinson win to a mid-single-digit Turek win, and the estimate has moved repeatedly in both directions over the past two weeks. A single survey that lands on a tie will move an average built on a race this evenly balanced, and the next one may move it back.

Iowa matters to the national picture because our Senate numbers are close to even. We give Democrats a 49 in 100 chance of winning Senate control and Republicans 50 percent, with a mean of 50.2 Democratic seats. 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. A seat our model prices near a coin flip is, on those thresholds, close to decisive.