Ohio Senate model shifts toward Husted, with Brown at 45 in 100

Our model now gives Sherrod Brown, the Democrat, a 45 in 100 chance of winning the Ohio Senate special election, and Republican Jon Husted, the incumbent, a 55 percent chance. A week ago, in our run dated August 21, those figures were reversed: Brown 59 percent, Husted 41 percent. That is a move of 14.1 points of Democratic win probability in seven days, toward the Republican.

The projected margin moved with it. Our previous run had a mean margin of D+1.6; this one has a mean margin of R+0.8. The middle of our distribution has crossed from one side of the line to the other, which is what turns a modest polling shift into a large probability shift in a race this close. Our 5th-to-95th percentile range now runs from R+11.4 to D+10.0, against R+9.4 to D+12.6 last week. Outcomes several points in either direction remain well inside that range.

We do not have a cause to offer. The payload for this run contains no new Ohio survey between August 21 and today, so the movement is our model's, and we are leaving the explanation open rather than assigning one.

Nationally, our generic ballot average stands at D+6.6 across 23 polls in a 45-day window. Our Senate numbers give Democrats a 43 percent chance of winning control, with a mean of 49.9 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. Ohio is one of the seats that separates those two outcomes.