Not all districts are created equal. They all count the same when adding for a majority, but victories in one type of district may portend a much better night for Democrats than in others. With just four days to go until Election Day, Democrats almost surely won’t gain the 30 seats needed for a House majority on Tuesday. But they will make some gains. Here’s where to watch for early clues as to just how big or small Democratic gains will be.

The Known Battlegrounds

To achieve double-digit gains, Democrats must win the known battlegrounds. These are the districts that always were going to be competitive, and where presidential year turnout usually gives Democrats an advantage. At the very least, Democrats need to win the districts that President Barack Obama carried — places like Illinois’ 10th District, Nevada’s 4th and 3rd Districts, Maine’s 2nd District, Florida’s 26th District, (which is now even more Democratic), Iowa’s 1st District and New York’s 19th District. If they’re not able to win these seats, Democratic gains in the House will likely be very minimal.  

[Democratic Gains in the House Depend on Clinton’s Success] 

But down-ballot Republicans in some of these original battlegrounds have proven remarkably resilient to Democrats’ attempts to tie them to Donald Trump. In New York’s 24th District, an Obama district, GOP Rep. John Katko has done a good job distancing himself from the top of the ticket and is likely to win over ticket-splitters who are also voting for Clinton.

The Trump Territories

Trump is actually making things harder for some down-ballot Democrats, even in districts Obama won. Rather than dragging down Republican candidates, the GOP presidential nominee is boosting some of them because he’s over-performing among their mostly white constituents compared to previous GOP presidential nominees.

[As Maine’s 2nd District Goes, so Goes the Nation?]

Democrats should have had sewn up Iowa’s 1st District months ago, for example. GOP Rep. Rod Blum, a member of the House Freedom Caucus, sits in a seat that Obama twice won by double digits, and yet he’s not as vulnerable as he was at the start of this year because Trump is doing well in his 90-percent-white district.

[In Trump Country, Democrats Fight to Defend Minnesota Seat]

Trump has also complicated Democrats’ efforts in two rematches. This should be Democrats’ year to knock off Rep. Bruce Poliquin, who won Maine’s 2nd District in a strong year for Republicans. The district typically votes Democratic, but Trump’s brand of populism is resonating with blue collar voters. There’s a similar effect for president going on in Minnesota’s 8th District, which also voted for Obama but is now Trump country. That means Democratic-Farmer-Labor Rep. Rick Nolan has to over-perform Clinton to defeat Republican Stewart Mills for a second time.

The Competitive Suburbs

If Trump is going to boost Democrats, it’s going to be in the well-educated suburbs where he’s deeply unpopular.Virginia freshman Rep. Barbara Comstock always was going to be a Democratic target. Her mostly affluent and suburban 10th district went for Obama narrowly in 2008 and Mitt Romney narrowly four years later. But Trump is not Romney. And Democrats have been tying Comstock to Trump non-stop in an effort to bring independent and GOP voters over to their recruit, LuAnn Bennett. A Bennett upset could portend a night of suburban women voting against Trump and Republicans all the way down the ticket.

[Suburban Brawl: The Fight Over Independents and Moderate Republicans]

Democrats have similar hopes for Colorado’s 6th District, another suburban community and perennial target. Rep. Mike Coffman has made Trump-like comments (questioning Obama’s citizenship in 2012), but he’s called on Trump to step aside and made a strong effort to court his increasingly diverse constituency. A Democratic victory here for state Sen. Morgan Carroll would be a good sign that their efforts to tie Republicans — even those who have disavowed Trump — to the nominee might be working, at least in places that favor Clinton.

The Reach Seats

With help from Trump, Democrats have succeeded in expanding the House battlefield into traditionally red districts. They’ve put some GOP incumbents who weren’t expecting tough races on the defensive.

[Democrats Aim to Reduce 30-Seat House Deficit with Help from Trump]

In Kansas’ 3rd District, which voted for Romney by 10 points, Democrats have spent money trying to tie Rep. Kevin Yoder to Trump and Gov. Sam Brownback. If Democrat Jay Sidie wins here, the party will be having a really great night. Minnesota’s 3rd District is more Democratic. But it fits in the same category of lower-tier races that, if they go Democrats’ way at the congressional level, could signal a wave.

[Even with Trump, Suburban District Is a Reach for Minnesota Democrats]

Trump is deeply unpopular in the Twin Cities suburbs, and Democrats argue that even if GOP Rep. Erik Paulsen doesn’t sound like Trump, he legislates like him. That’s a tough sell against Paulsen, who has a history of over-performing the top of the GOP ticket.