A day before the midterms, Democrats appear poised for a suburban wave.

Thanks to President Donald Trump's terrible approval ratings among college-educated women, a historic number of GOP open seats and staggering Democratic fundraising, Democrats remain favorites to pick up the 23 seats they need for House control.

But it's still not a done deal.

Republicans point to rising overall approval numbers for Trump (46 percent in the new NBC/Wall Street Journal survey), strong jobs numbers and a narrowing Democratic voting enthusiasm advantage as evidence that they could still hang on. But at the district level, their list of problems has continued to grow.

In the final stretch, Republican polling numbers haven't gotten any better in upscale suburban "Whole Foods" districts where members like Rep. Barbara Comstock of Northern Virginia, Rep. Erik Paulsen of Minnesota, Rep. Mike Coffman of Colorado and Rep. Kevin Yoder of Kansas continue to trail.

At the same time, there is some evidence that GOP fortunes have marginally improved in "Trump Zone" districts where the president won by double digits in 2016 — places like downstate Illinois, upstate New York and the Iron Range of Minnesota.

However, the most noticeable pattern in the last three weeks has been a shift toward Democrats in middle-income outer suburbs that voted for Trump by single digits in 2016, including districts represented by Rep. Randy Hultgren of Illinois, Rep. Mike Bishop of Michigan and Rep. Mia Love of Utah.

Two weeks ago, I identified nine types of races that will decide the House's fate. The battleground has expanded slightly since then and spans many different slices of America — from Alaska to the professional suburbs of Atlanta. Here's a breakdown of what we estimate Democrats need in each of these nine categories to prevail on Tuesday:

1. Vulnerable Dem Open Seats

If Republicans are going to hold their majority, they'll need to succeed on offense. Most Democratic incumbents are in excellent shape, but the party holds five at-risk open seats. 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 two of five.

2. Republicans in White-Collar Suburbs Won by Clinton in '16

Democrats' "blue wave" is most super-charged in elite, professional suburbs where Trump is woefully unpopular with college-educated voters, particularly women. Ten GOP incumbents are at risk in Clinton-won districts, including areas such as Orange County, California, and the suburbs of Chicago, Dallas and Kansas City. Rep. Barbara Comstock in Northern Virginia is the single most likely to lose. Democrats probably need: to flip seven of 10.

3. GOP Open Seats Won by Clinton in '16

It's not just a "blue wave," it's a "red exodus": There are 41 open or vacant Republican seats, the most since at least 1930. Of those, the most problematic for the GOP are the eight districts Clinton carried in 2016. 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. One of Republicans' better opportunities to hang on to one of these seats is in Florida's 27th District, a 76 percent Hispanic district where Democrats nominated former HHS Secretary Donna Shalala, who doesn't speak Spanish. Democrats probably need: to flip seven of eight.

4. GOP Open Seats Won by Trump in '16

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, and two districts where Republican incumbents lost primaries: Rep. Robert Pittenger's seat in North Carolina and Rep. Mark Sanford's seat in South Carolina.

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 racial 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 four of 12.

5. Republicans in Bellwether Suburbs

Ten vulnerable GOP incumbents represent 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, Illinois' 14th 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 three of 12.

6. Republicans in Majority Nonwhite Districts

Another six Republicans represent districts where majorities of their constituents are nonwhite. All but Georgia's 7th District voted for Clinton in 2016. Democrats' challenge is that some of these incumbents are personally popular and Latino turnout typically plummets in midterms. Rep. Will Hurd in Texas's 23rd District is probably in the best shape, in part thanks to his vocal criticism of the president on immigration. Democrats probably need: to flip two of eight.

7. Republicans Representing 'Trump Surge Zones'

Six vulnerable Republicans represent heavily white, working-class districts that previously voted for Barack Obama but swung hard to Trump in 2016. Rep. Rod Blum in northeastern Iowa is the most vulnerable, but Rep. Mike Bost in Illinois and Rep. Bruce Poliquin in Maine are also in serious jeopardy. These are places where the Kavanaugh fight may have boosted the GOP, especially in upstate New York. Democrats probably need: to flip two of six.

8. Republicans in Districts with Urban/Rural Divides

Democrats have pickup chances in 12 districts that combine midsize cities and large rural components. In a big wave, the risk for Republicans is that energized Democrats in cities like Des Moines, Iowa; Little Rock, Arkansas; and Spokane, Washington, turn out at sky-high rates while voters in red, rural surrounding areas stay home. Rep. David Young in Iowa is probably at the greatest risk. Democrats probably need: to flip one of 12.

9. Republicans with Self-Inflicted Wounds

Finally, there are seven Republicans who have no one to blame but themselves for their political woes in Trump-won districts. They include Reps. Duncan Hunter of California and Chris Collins of New York, whose ruby-red seats wouldn't otherwise be in play if it weren't for the fact they are running for re-election under indictment.

New on this list: Rep. Steve King of Iowa, whose comments on race and travels to Europe to meet with far-right political figures have drawn condemnations from members of both parties. Still, in this polarized political era, Democrats would need a tsunami to beat any of them. Democrats probably need: None; any of these seats would be icing on their cake.