Senate sits at a coin flip in our model as the House holds at 97 percent

Forty-five days out, our model gives Democrats a 51 in 100 chance of winning Senate control and Republicans a 48 percent chance. The mean Democratic seat count is 50.5. Democrats need 51 seats for a majority and Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to the Republicans. That asymmetry is most of why a forecast averaging half a seat above 50 still splits close to even.

The House is steadier. Our model puts the Democratic chance of a majority at 97 percent against 3 percent for Republicans, with a mean of 242.7 seats and 218 needed. One caveat is ours to own: our simulation draws error at four correlated levels — national, census division, state and district — but has no cluster term linking demographically similar districts across state lines. Without that, the House control number is marginally firmer than a fuller decomposition would leave it. We have not measured how much, so we are not putting a figure on it.

Our generic ballot average is D+7.3, drawn from 28 polls over the past 45 days. A John Zogby Strategies survey of 1,007 likely voters, fielded September 15-17, had Democrats at 48 percent and Republicans at 42.

Minnesota accounts for the largest single-day change on our board, with the Democratic win probability there down 17.9 points, from 91 percent to 73 percent. Kansas moved the other way, up 13.3 points to 23 percent, after an Emerson College survey for The Hill of 750 likely voters, fielded September 15-16, found Roger Marshall at 43.3 percent and Democrat Adam Hamilton at 44.8, with 3.7 percent for other candidates — a close race. Iowa eased 5.2 points to 42 percent for Democrats; a co/efficient poll of 831 likely voters, fielded September 14-16, had Ashley Hinson at 46 percent and Josh Turek at 42. Texas rose 4.3 points to 72 percent, and Florida and North Carolina both improved for Democrats, movements this site covered yesterday.

Elsewhere in the recent field work, InsiderAdvantage surveyed 1,200 Michigan likely voters September 16-17 and found Abdul El-Sayed at 46.6 percent and Mike Rogers at 44.7, with 1.1 percent other — close enough that the poll does not separate them. Trafalgar Group polled 1,085 Ohio likely voters September 14-16 and had Sherrod Brown at 45.4 percent and Jon Husted at 41.5. In Alaska, co/efficient polled 799 likely voters September 14-17 and found Dan Sullivan at 49 percent to Mary Peltola's 46. Our model's Senate probabilities are estimates of chance, not projections of who finishes ahead, and at 51-48 the chamber remains the least settled part of the board.