New Iowa Senate poll shows a close race, and our forecast is unchanged

A Suffolk University survey of 500 likely voters in Iowa, fielded August 20-23, put Republican Ashley Hinson at 45 percent and Democrat Josh Turek at 41 percent. That is a four-point gap on a sample of that size, which is close enough that the poll does not establish who is ahead. Roughly one in seven respondents chose neither candidate.

The poll did not move our numbers. Our model gives Turek a 22 in 100 chance of winning the seat and Hinson 78 percent, the same split as our previous run earlier on August 26. The mean margin shifted from R+5.1 to R+5.0. Our 5th-to-95th percentile range runs from R+15.8 to D+5.7, so outcomes from a comfortable Republican win to a narrow Democratic one remain inside it. This is an open seat; the incumbent, Republican Joni Ernst, is not on the ballot.

Iowa matters to the wider picture. Our model gives Republicans a 55 percent chance of winning Senate control and Democrats 45 percent, with a mean of 50.0 Democratic seats. Democrats need 51 seats for a majority and Republicans 50, because the vice president is a Republican and a 50-50 tie goes to their side. A race our model has at 22 percent for the Democrat is not the likeliest path to 51, but the distribution here leaves it live.

The House picture is more lopsided. Our model gives Democrats a 93 percent chance of a majority there, with a mean of 241 seats against the 218 needed, and our national generic-ballot average stands at D+6.5 across 27 polls over the past 45 days. One caveat on the House figure is ours: our simulation correlates error nationally, by census division, by state and by district, but we have no data to correlate demographically similar districts across state lines, so that 93 percent is somewhat firmer than a fuller accounting would leave it.