Democrats at 53 percent for the Senate and 99 percent for the House in our model

With 33 days until the November 3 election, our model gives Democrats a 53 in 100 chance of winning control of the Senate and Republicans a 47% chance. Our simulations put the Democrats' average at 50.5 seats. Democrats need 51 seats for control. Republicans need 50, because the vice president is a Republican and a 50-50 tie goes to them.

Our model gives Democrats a 99% chance of winning a House majority, with an average of 245.3 seats against the 218 needed. That figure is somewhat firmer than it should be. Our simulation correlates error nationally, by census division, by state and within each district. It does not yet link demographically similar districts in different parts of the country, because we lack the data to do so, and that omission narrows the spread of outcomes slightly.

Our generic ballot average is D+8.2, built from 30 polls over a 45-day window. Recent entries vary. A YouGov survey for the Economist of 1,423 registered voters, fielded September 25-28, had Democrats at 45% and Republicans at 37%. A HarrisX/Harris Poll survey for Harvard CAPS, fielded September 26-28, found a 50-50 tie among 2,200 registered voters and a close 51-49 Democratic edge among likely voters.

Several Senate races moved in our forecast. The Democratic chance in Ohio rose from 60% to 75%, the largest change on the board. Minnesota went the other way, from 85% to 72%. An InsiderAdvantage survey of 1,200 likely voters there, fielded September 28-29, found a close race, with the Democrat at 46% and the Republican at 45%. The Democratic chance in Florida fell from 30% to 20%. Michigan rose from 70% to 77%. Kansas edged up from 18% to 21%. Maine moved from 51% to 60%.

In Iowa, a Quantus Insights survey of 738 likely voters, fielded September 28-29, found a close race. Republican Ashley Hinson had 48.5% and Democrat Josh Turek had 46.6%. In a head-to-head version of the same survey, Hinson had 51.2% and Turek had 48.8%. In New York's 17th District, an Emerson College survey for PIX 11 of 400 likely voters, fielded September 27-29, also showed a close race. Democrat Cait Conley had 47.9% and Republican Mike Lawler had 45.6%.