New Ohio poll puts Brown up 5, and our estimate moves to 70 in 100

An InsiderAdvantage survey of 1,200 likely voters in Ohio, fielded September 8-9, put Sherrod Brown at 47.3 percent and Republican incumbent Jon Husted at 41.9 percent, a margin of 5.4 points for the Democrat.

Our model now gives Brown a 70 in 100 chance of winning the special election, with a mean margin of D+3.3 and a 5th-to-95th percentile range running from R+6.8 to D+13.4. That is a reversal from our previous run, at 4:32 PM ET on September 10, which had Brown at 39 percent, Husted at 61 percent and a mean margin of R+1.8 within a range of R+11.8 to D+8.3.

The change is the work of this single survey. Ohio has been the most unsettled race on our board: we published a movement note on September 7 that had Brown at 41 in 100, after a poll reaction on August 31 that had him at 56 in 100 and earlier notes in August at 45 and 58. The new number does not settle that pattern so much as extend it. Our range still contains outcomes on both sides by several points, and a race whose central estimate has crossed the midpoint four times in three weeks is one where the next survey carries a lot of weight.

The seat matters for the chamber arithmetic. 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 need 50, because the vice president is a Republican and a 50-50 tie goes to them. Nationally, our generic-ballot average stands at D+6.7 across 25 polls in the last 45 days.