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.