Cooper's chances in North Carolina rise to 87 percent in our model

Our model gives Roy Cooper, the Democrat, an 87 in 100 chance of winning the open North Carolina Senate seat, up from 79 percent in our run of September 3. That is a gain of eight points of win probability over seven days. Michael Whatley, the Republican, is at 13 percent.

The projected margin moved with it. Our mean margin is now D+6.8, against D+5.0 a week ago. The spread narrowed slightly on the Republican side and widened on the Democratic side: our 5th-to-95th percentile range runs from R+3.3 to D+16.8, where last week it ran from R+5.4 to D+15.4. A Republican win remains inside the range our simulations produce.

Four surveys entered the average in that span. East Carolina University's Center for Survey Research polled 675 likely voters from August 31 to September 3 and had Cooper at 51.7 percent and Whatley at 43.6 percent. YouGov, for Elon University, fielded August 21-31 and reported Cooper ahead in all three of its samples: 49 to 38 among 565 likely voters, 49 to 36 among 677 registered voters, and 39 to 29 among 800 adults. All four point the same direction, and together they account for most of the week's shift.

The national picture is less settled than the state one. Our model gives Democrats a 41 percent chance of Senate control and Republicans 58 percent, with a mean of 49.8 Democratic seats. Democrats need 51 seats for control; Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to them. Our generic-ballot average, drawn from 24 polls over the past 45 days, stands at D+6.5. A high probability in one state does not carry the chamber.