House Race Ratings by the Cook Political Report

Democrats must flip at least 23 Republican-held seats to retake the House this November. There are currently 75 highly competitive seats — those considered a tossup between the two parties or leaning slightly toward one — according to race ratings provided by the Cook Political Report , a nonpartisan election handicapper.

Here’s the latest.

Republicans have improved their position in a few districts with significant rural communities, in areas outside Cincinnati and St. Louis, where conservative support has coalesced in recent weeks behind Mr. Trump and his party. And Republicans are likely to pick up a Democratic-held seat in northern Minnesota. If they do, Democrats would have to offset that loss by winning one more Republican-held seat, in order to win a majority.

There are an additional 56 Republican-held seats that are vulnerable, rated either as toss-ups or as leaning slightly to the right. Many are in red-state suburbs, near cities like Dallas, Salt Lake City and Raleigh, N.C., or in more rural parts of the country. Republicans must win nearly 90 percent of those seats to keep control.

Democrats must net a 23-seat gain in order to take power in the House, and there are now 17 districts currently held by Republicans that are leaning slightly or strongly toward Democratic candidates. These seats are mainly in affluent suburban areas, including half a dozen seats just in New Jersey and Pennsylvania.

The map of competitive House races has only continued to grow in the final month of the 2018 campaign, leaving Republicans scrambling to contain Democratic gains in even conservative-leaning areas. Republicans could still keep control of the House by a slim margin, but they would have to win the overwhelming majority of competitive races in order to hang on.

The list of close-run House races keeps growing as the midterm elections draw nearer, as Democrats keep putting Republicans on defense in traditionally conservative-leaning areas. Since August, the number of pure toss-up races — where both parties have a roughly even chance of winning — has grown to 30, including 28 seats currently held by Republicans. And there are nine Republican-held seats that currently lean toward the Democrats, up from seven a month ago. Democrats must gain a total of 23 seats to take the majority.

Most of the changes to the electoral map have come in once-safe Republican areas — like the suburbs of St. Louis and Charlotte, N.C., or rural southern New Mexico. These areas have become more vulnerable for the party because of President Trump’s unpopularity, especially with moderates and women. And seats in two solid-red districts, outside Buffalo, N.Y., and in San Diego, have become competitive because Republican lawmakers in both districts were indicted for corruption.

There were only a few encouraging shifts for Republicans, but they were important ones, including a Republican-held open seat in Miami that shifted back into the toss-up category after being seen for months as lost to the Democrats.

All together, there are now 64 Republican-held seats that are seriously contested, up from 58 in the middle of August.

Nearly all of these races remain very close, and a new shift in the national environment could tip many of them in either direction come Election Day. But the size of the battlefield matters a lot: The more Republican-held seats in play, the smaller the percentage of those seats Democrats need to win in order to gain power.