Senate control sits at even money as Maine and Ohio estimates move

Fifty days out, our model splits Senate control down the middle: a 50 in 100 chance of a Democratic majority and the same for Republicans, as of 6:32 AM ET on September 14. The mean outcome in our simulations is 50.3 Democratic seats. Democrats need 51 for a majority and Republicans need 50, because the vice president is a Republican and a 50-50 chamber goes to the Republicans.

The House is not close in our numbers. Our model gives Democrats a 95 percent chance of winning a majority, against 4 percent for Republicans, with a mean of 240.9 seats and 218 needed. One caveat is ours to own: our simulation draws correlated error nationally, by census division, by state and by district, but not across demographically similar districts in different places, because we have no cluster data for that term. Without it, the House control probability is modestly firmer than a fuller decomposition would leave it. We have not measured the size of the gap, so we are not putting a figure on it.

Our generic ballot average stands at D+6.8, drawn from 22 polls over the past 45 days. Two of the more recent readings sit on either side of it. A YouGov survey for CBS News of 1,750 likely voters, fielded September 8-11, had Democrats at 54 percent and Republicans at 46. An ActiVote poll of 1,000 likely voters, fielded August 31 to September 10, had it 52.3 to 47.7.

The largest single-race move in the past week was in Maine, where our estimate of the Democratic win probability fell 21 points, from 90 percent to 69. Ohio moved 19.5 points the other way, from 42 percent to 61, alongside an InsiderAdvantage poll of 1,200 likely voters fielded September 8-9 that put Sherrod Brown at 47.3 percent and Jon Husted at 41.9. South Carolina moved up 8.2 points to a 15 percent Democratic chance. Our Iowa, North Carolina and Texas estimates also shifted this week and are covered separately.

Elsewhere in the Senate polling, a Quantus Insights survey of 733 Florida likely voters, fielded September 8-10, had Republican Ashley Moody at 50.4 percent and the Democrat at 43. The same pollster's Minnesota poll of 720 likely voters over the same dates had the Democrat at 48.9 and the Republican at 45.4. A co/efficient poll of 915 Kansas likely voters, fielded September 8-10, had Roger Marshall at 49 percent and Adam Hamilton at 44. Three races registered as close: Trafalgar Group's Michigan poll of 1,079 likely voters, fielded September 7-9, had Abdul El-Sayed at 46.3 and Mike Rogers at 44.8; Public Policy Polling's South Dakota survey of 629 registered voters, fielded September 8-9, had Mike Rounds at 45 and independent Brian Bengs at 42.