New Quantus poll in OH-1 leaves our forecast essentially where it was

A Quantus Insights survey of 509 likely voters in Ohio's 1st District, fielded August 21-24, puts Democratic incumbent Greg Landsman at 47.9 percent and Republican Eric Conroy at 44.6 percent. The gap is small enough on that sample size that the poll describes a close race rather than a clear lead.

Our forecast did not move much. The model now gives Landsman a 93 in 100 chance of winning the seat, with a mean margin of D+15.0 and a 5th-to-95th percentile range running from R+1.5 to D+31.1. The previous run, earlier the same afternoon, had 94 percent, D+15.3, and a range of R+1.3 to D+31.5. That is a shift of a single point in the win probability and three tenths of a point in the expected margin.

The distance between the poll and the model average is the notable feature here, and it is not new. Our projected margin remains far wider than the 3.3-point difference Quantus Insights measured, and the model's lower tail already allows for a narrow Republican win: the 5th percentile outcome is R+1.5. One district poll of about 500 respondents carries limited weight against that, which is why the run barely changed.

Nationally, our average of 28 generic-ballot polls over the past 45 days stands at D+6.5. The model gives Democrats a 93 percent chance of winning a House majority, with a mean of 240.1 seats against the 218 needed. One caveat on that 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. Without that term, the House control number is marginally firmer than it would otherwise be.