Maine moves toward the middle as Ohio odds tip to Brown in our forecast

Our model gives Democrats a 49 in 100 chance of a Senate majority and Republicans a 50 percent chance, with a mean of 50.3 Democratic seats as of 6:32 a.m. ET. 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. In the House, our model puts the Democratic chance of a majority at 95 percent and the Republican chance at 5 percent, with a mean of 240.6 Democratic seats against the 218 needed.

That House figure carries a caveat of our own making. Our simulation draws error at four correlated levels: national, census division, state and district. It does not include a term linking demographically similar districts in different places, because we have no cluster data for one. The effect is that our House control number is marginally firmer than a fuller decomposition would leave it. We have not measured the size of that gap for this run, so we are not adjusting the figure.

Our generic ballot average stands at D+6.7, drawn from 22 polls over the past 45 days. The newest is an ActiVote survey of 1,000 likely voters fielded August 31 to September 10, which had Democrats at 52.3 percent and Republicans at 47.7 percent.

The largest move in the past day was in Maine, where the Democratic win probability in our model fell 23 points, from 90 percent to 67 percent. Ohio moved the other way, up 19.5 points to 63 percent, after an InsiderAdvantage survey of 1,200 likely voters fielded September 8-9 put Sherrod Brown at 47.3 percent and Jon Husted at 41.9 percent. Our Iowa estimate rose 12.5 points to 47 percent, North Carolina rose 7.1 points to 84 percent, South Carolina rose 8.6 points to 15 percent and Kansas rose 4.2 points to 9 percent.

Several of the closest results came from the same field period. In Michigan, a Trafalgar Group poll of 1,079 likely voters fielded September 7-9 had Abdul El-Sayed at 46.3 percent and Mike Rogers at 44.8 percent, a close race. InsiderAdvantage's Texas poll of 1,200 likely voters, fielded September 8-9, had James Talarico at 47.1 percent and Ken Paxton at 45.6 percent, also close, as was its South Carolina poll of 1,200 likely voters, with Republicans at 45.1 percent and Annie Andrews at 43.2 percent. Public Policy Polling's South Dakota survey of 629 registered voters, fielded September 8-9, had Mike Rounds at 45 percent and independent Brian Bengs at 42 percent. Florida drew two readings: Quantus Insights, polling 733 likely voters on September 8-10, had Ashley Moody at 50.4 percent and the Democrat at 43 percent, while Change Research, polling 1,107 likely voters for Freedom Project USA on September 7-9, had the race tied at 47. Quantus also had Minnesota Democrats at 48.9 percent to 45.4 percent among 720 likely voters.