Senate stays near even as our House number holds at 98 percent

With 40 days until the November 3 election, our model gives Democrats a 51 in 100 chance of winning Senate control and Republicans a 49 percent chance. The mean Democratic seat count in our simulations is 50.5. Democrats need 51 seats for a majority; Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to them. Those numbers are as of 6:32 a.m. ET on September 24.

The House is further from the line. Our model gives Democrats a 98 percent chance of winning a majority and Republicans 2 percent, with a mean of 245.5 Democratic seats against the 218 needed for control. One caveat on that figure is ours to own: our simulation draws correlated error nationally, by census division, by state and within each district, but it has no term linking demographically similar districts in different places, because we have no cluster data for this run. The House probability is therefore marginally firmer than a fuller error model would make it, by an amount we have not measured.

Our generic ballot average stands at D+8.1, drawn from 30 polls over the past 45 days. The most recent national surveys are spread around that. A YouGov poll for the Economist of 975 likely voters, fielded September 18-21, had Democrats at 52 percent and Republicans at 38; the same pollster's registered-voter sample of 1,394 had it 45-36. Echelon Insights, polling 1,002 likely voters September 17-21, had Democrats at 51 and Republicans at 43. Verasight, for Strength In Numbers, had Democrats at 52 and Republicans at 42 among likely voters fielded September 16-21, and 50-42 among 1,374 registered voters. ActiVote, polling 1,000 likely voters September 11-21, had Democrats at 52.8 and Republicans at 47.2.

Six Senate races moved in our latest run. Iowa moved 17.2 points toward the Democrat, from a 42 percent chance to 59 percent. Minnesota moved 16.7 points, from 68 percent to 85 percent. Texas moved 15 points the other way, from 70 percent to 55 percent, and Ohio moved 12 points down, from 72 percent to 60 percent. Kansas rose 9.2 points, from 9 percent to 18 percent, and remains the least likely of the six for the Democrat.

North Carolina moved 10 points toward the Democrat, from 84 percent to 94 percent, after a Quantus Insights survey of 686 likely voters fielded September 21-22 put Roy Cooper at 48.4 percent and Michael Whatley at 43.3 percent, with 0.5 percent for others. That is the largest Democratic probability among the races that moved.