Senate at 44-55 for Democrats; House estimate holds near 240 seats

Fifty-nine days from the November 3 election, our model gives Democrats a 44 in 100 chance of winning a Senate majority and Republicans a 55 percent chance. The mean Democratic seat total across our simulations is 50.0. Democrats need 51 seats for control; Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to their party. That is a one-point shift toward Republicans from the 45-54 split this site published on September 4.

In the House, our model gives Democrats a 93 percent chance of a majority and Republicans 6 percent, with a mean of 239.5 Democratic seats against the 218 needed for control. Our simulation draws error at four correlated levels: one national, one per census division, one per state, and each district's own. It does not include a term linking demographically similar districts wherever they sit, because we have no cluster data for one. The consequence is that our House control probability is marginally firmer than a fuller decomposition would make it. That gap is not measured in this run, so we are not putting a figure on it.

Our generic ballot average is D+6.3, drawn from 25 polls fielded within the past 45 days. Recent surveys vary in level. Morning Consult, polling 28,429 registered voters August 24-30, had Democrats at 47.1 percent and Republicans at 42.3 percent. YouGov, for the Economist, had Democrats ahead 46 to 40 among 1,434 registered voters fielded August 28-31, and 36 to 31 among 1,589 adults over the same dates. Ipsos, for Reuters, had 43 to 38 among 924 registered voters and 38 to 31 among 1,167 adults, both fielded August 28-31. HarrisX, for Harvard CAPS, had a closer split over August 28-30: Democrats 51 to 49 among 2,100 registered voters, and Republicans 51 to 49 among likely voters.

Six races moved in our forecast. Democratic win probability fell 21 points in OH-7, from 51 percent to 30 percent, and 16.3 points in TX-15, from 52 percent to 36 percent. It rose 14.3 points in the Iowa Senate race, from 22 percent to 36 percent, and 10.8 points in the Michigan Senate race, from 58 percent to 69 percent. It fell 10 points in South Carolina, to 7 percent, and 9.6 points in New Hampshire, to 81 percent.

Emerson College, polling for Nexstar, put Ashley Hinson at 49 percent and Josh Turek at 45 percent among 750 Iowa likely voters fielded August 31 to September 1. In New Hampshire, Fabrizio, Lee & Associates, polling 600 likely voters August 27-30 for the National Republican Senatorial Committee, put Chris Pappas at 36 percent; the results in our database list no share for a Republican candidate, so no margin can be stated. In TX-35, Normington, Petts & Associates, polling likely voters August 27-31 for House Majority PAC, had Republican Carlos De La Cruz at 45 percent and Democrat Johnny Garcia at 44 percent, a result too close to call a lead.