Cygnal poll has Iowa Senate tied, and our estimate does not move

A Cygnal Political survey of 500 likely voters in Iowa, sponsored by the Iowans for Tax Relief Foundation and fielded September 9-11, put Democrat Josh Turek and Republican Ashley Hinson level at 42.9 percent each, with 3.6 percent for other candidates. That is a tie, and it is the only new number in this race.

Our model is unchanged by it. It gives Turek a 45 in 100 chance of winning the seat and Hinson 55 percent, the same split as our previous run earlier today. Our mean margin is still R+0.8. The only difference is at the edge of the distribution: our 5th-to-95th percentile range now runs from R+10.6 to D+9.1, against R+10.7 to D+9.1 before. The seat is open; Joni Ernst, the Republican incumbent, is not on the ballot in our candidate list.

The practical read is that this poll confirms rather than changes. Our average already had the race within a point, and a tied sample of 500 voters sits close to the middle of that. The distribution remains wide enough on both sides that neither candidate is favored by much in our numbers.

Iowa matters to the chamber arithmetic. Our model has Democrats averaging 50.1 Senate seats, with 51 needed for a Democratic majority and 50 enough for Republicans, because the vice president is a Republican and a 50-50 tie goes to them. That leaves Democratic control of the Senate at 48 percent and Republican control at 52 percent. In the House our model gives Democrats a 95 percent chance of a majority, with a mean of 241.1 seats against the 218 needed; that figure is marginally firmer than it should be, because our simulation correlates district error nationally, by census division and by state, but has no data to correlate demographically similar districts across state lines.