WASHINGTON — With 95 days to go until Election Day, the House majority is up for grabs.
President Donald Trump's below-average approval ratings, Democrats' enthusiasm edge and a historic number of GOP open seats make Democrats the slight favorites to take control in the lower chamber. But what's their route to picking up the 23 seats they need?
As Republican groups prepare to raise and spend over $100 million to prevent a Democratic takeover, the race-by-race battleground is coming into focus. The Cook Political Report rates 60 GOP-held seats and just five Democratic-held seats as at-risk — meaning Democrats need to win 28 of those 65 to win control.
We've identified eight types of races that will decide the House's fate. The battleground is wide and spans many different slices of America — from the professional suburbs of Minneapolis to the coalfields of southern West Virginia.
Here's a breakdown of what we estimate Democrats need in each of these eight categories to prevail in November.
Note: The Cook Political Report's Partisan Voter Index, or PVI, is a metric of how much more Democratic or Republican a district has voted in the last two presidential elections compared to the nation as a whole.
Category 1: Races with Democratic departures
Democrats' path to a majority starts with protecting their own vulnerable seats. Most of their incumbents are in excellent shape, but the party holds five open seats in districts that Trump carried in 2016. Of those, they're sure to lose Pennsylvania's 14th District, which Rep. Conor Lamb is leaving to run in a nearby seat after the state's map was redrawn. The next two most vulnerable open seats are in rural Minnesota.
Democrats probably need: To hold 3 of 5.
Category 2: Clinton districts that saw a red exodus
There are 42 open or vacant Republican seats, the most since at least 1930. Of those, the most problematic for the GOP are the eight districts Hillary Clinton carried in 2016. In these seats, history is working against the GOP: Since 1992, in situations when a president's party was stuck defending an open seat two years after the president failed to carry it, that party has batted zero for 23 keeping it in their column.
Democrats are almost guaranteed to pick up Pennsylvania's 5th and 6th Districts after the state's Supreme Court redrew them in February to be much more heavily Democratic. Republicans' best opportunity to hold on to one of these seats is in Washington's 8th District, where a well-known GOP businessman, Dino Rossi, has a financial head start over a divided Democratic field.
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Democrats probably need: to flip 7 of 8.
Category 3: White-collar wonderlands souring on Trump
Democrats' path to the majority depends on running up the score in elite, professional suburbs that are rapidly souring on the GOP in the Trump era. Ten GOP incumbents are at risk in highly college-educated districts Clinton carried in 2016: places like Orange County, California, and the suburbs of Chicago, Dallas and Kansas City, Missouri. Rep. Barbara Comstock in Virginia's 10th District is the single most vulnerable.
Democrats probably need: to flip 5 of 10.
Category 4: Diverse Clinton districts represented by GOP
Another five at-risk Republicans represent highly diverse districts Clinton carried. Democrats' challenge is that these incumbents tend to be personally popular and Latino turnout typically plummets in midterms. Reps. Carlos Curbelo in Florida's 26th District and Will Hurd in Texas's 23rd District are probably in the best shape to survive a wave, thanks to their vocal criticism of the president on immigration.
Democrats probably need: To flip 2 of 5.
Category 5: Trump districts that saw a red exodus
There are 11 more highly vulnerable Republican open seats that Trump carried, ranging from a seat he won by a point (New Jersey's 11th District) to one he carried by 50 points (West Virginia's 3rd District). They include Speaker Paul Ryan's seat in Wisconsin, next week's high-stakes special election in Ohio's 12th District and Virginia's 5th District, where the GOP nominee came under fire this week for his Bigfoot-related social media posts.
Democrats are virtually guaranteed to pick up New Jersey's 2nd District, where popular moderate Rep. Frank LoBiondo is retiring and national Republicans withdrew support for their nominee upon learning of his comments critical of diversity. They're also well-positioned to pick up New Jersey's 11th District, where Appropriations Chairman Rodney Frelinghuysen chose not to seek re-election.
Democrats probably need: To flip 3 of 11.
Category 6: Districts where Trump surged in 2016
Polling shows Democrats in a surprisingly strong position in seven heavily white, working-class districts that swung hard toward Trump in 2016 (five of them voted for Obama in the past). Reps. Mike Bost in southern Illinois and Rod Blum in eastern Iowa are most vulnerable, and Reps. Greg Gianforte in Montana and Claudia Tenney in upstate New York have been their own worst enemies.
Democrats probably need: to flip 3 of 7.
Category 7: Races in bellwether suburbs
There are a dozen vulnerable GOP incumbents from suburban districts Trump carried by a single digit margin in 2016, and most represent a mix of professional and middle-class voters. Several, like Georgia's 6th District, Michigan's 8th District and Ohio's 1st District, were gerrymandered to protect Republicans, but political trends have caused the GOP's advantage to unravel.
Democrats probably need: to flip 3 of 12.
Category 8: Trump districts with an urban-rural divide
Democrats have pickup opportunities in seven districts Trump won that include both mid-size cities and large rural components. The risk for Republicans in these seats is that energized Democrats in cities like Des Moines, Iowa; Little Rock, Arkansas; and Spokane, Washington, turn out at sky-high numbers while voters in red, rural surrounding areas stay home. Reps. David Young in Iowa and Andy Barr in Kentucky are at the greatest risk.
Democrats probably need: to flip 2 of 7.
Bonus category: Blue tsunami watch
If Democrats are winning any of these long-shots seats on Election Night, the House is probably already a lost cause for Republicans. Yet not all of these races are looking secure for Republicans. For example, Democratic Air Force combat pilot M.J. Hegar has raised $1.6 million against 76-year old GOP Rep. John Carter in Texas's 31st District.
Democrats probably need: None; winning any of them would be icing on their cake.
David Wasserman, House editor for The Cook Political Report, is an NBC News contributor and senior analyst with the NBC Election Unit.