Model trims Sherrod Brown's edge in Ohio Senate race to 58 in 100

Our model now gives Sherrod Brown a 58 in 100 chance of winning the Ohio Senate special election, and Jon Husted, the Republican incumbent, a 42 percent chance. On our previous run, at 10:15 p.m. ET on August 16, the same race stood at 67 percent for Brown and 33 percent for Husted. That is a shift of 8.4 points of Democratic win probability toward the Republican over four days.

The expected margin moved with it, but by less. Our model puts the mean margin at D+1.4, against D+3.0 five days ago. The spread narrowed slightly at both ends: our 5th-to-95th percentile range now runs from R+9.4 to D+12.4, where before it ran from R+8.3 to D+14.1. Both versions of the race describe a contest close enough that either candidate winning would be an ordinary outcome.

No new Ohio survey appears in this payload. We cannot point to a poll that produced the change, and we are not going to guess at one. The model moved; the cause is not documented here. Movement of this size at a distance of 74 days from the November 3 election is within the range of what our runs produce as inputs, weights and national conditions update.

The national picture our model draws on has Democrats at D+6.7 in our generic-ballot average, built from 24 polls over a 45-day window. In the Senate as a whole, our model gives Democrats a 48 percent chance of winning control and Republicans 52 percent, with a mean of 50.2 Democratic seats. Democrats need 51 seats for control and Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to the Republicans. Ohio is one of the seats that separates those two outcomes.