Model trims Cooper's edge in North Carolina Senate race to 80 percent

Our model now gives Roy Cooper, the Democrat, an 80 in 100 chance of winning North Carolina's open Senate seat. A week ago, in the run dated Aug. 24, it gave him 88 percent. That is a move of eight points toward the Republican, Michael Whatley, over seven days.

The projected margin moved with it. Our model's mean margin is now Cooper by 5.4 points, down from 7.7 points in the previous run. The spread of simulated outcomes also shifted: our 5th-to-95th-percentile range runs from Whatley by 5.0 points to Cooper by 15.8 points, against a prior range of Whatley by 3.4 to Cooper by 18.6.

No new North Carolina Senate poll arrived between the two runs. The most recent surveys in our database are High Point University's Aug. 3-12 polls, which had Cooper ahead 50-45 among 660 likely voters and 48-41 among 800 registered voters, and a Harper Polling survey of 600 likely voters for Carolina Journal, fielded Aug. 9-10, with Cooper at 51.5 percent and Whatley at 39 percent. All predate the Aug. 24 run. The change therefore comes from elsewhere in the model rather than from fresh state polling, and we are not going to attribute it to a cause the payload does not contain.

The seat matters to our national picture, which is close. Our model gives Democrats a 49 percent chance of Senate control and Republicans 50 percent, with a mean of 50.2 Democratic seats. Democrats need 51 seats for control and Republicans 50, because the vice president is a Republican and a 50-50 tie goes to the Republicans. Our generic-ballot average, from 28 polls over the past 45 days, stands at D+6.5.