In one sense, Biden’s success in winning more districts (about 223) than Obama in 2012 (209) and Hillary Clinton in 2016 (205) constitutes clear progress for Democrats, reflecting the expansion of the party’s support in white-collar suburbs. But it still highlights the constraints on the Democrats’ reach: Trump won more House seats (230) in 2016 while losing the popular vote, and George W. Bush in 2004 won many more (256) while winning slightly less of the national vote than Biden did this year.

Those disparities explain why many analysts in both parties believe Democrats face a natural disadvantage in the House, even before factoring in gerrymandering.

“If you apportion the House in a fair drawing, it favors Republicans, because Democrats live in these urban enclaves that are 80 percent [Democratic] and they waste a lot of votes,” Tom Davis, a former Republican representative from Northern Virginia who chaired the National Republican Congressional Committee, told me.

The consequences of this imbalance are growing more significant because, as in Senate races, it’s getting harder for either party to win House seats in areas that vote the other way at the presidential level—especially in a presidential-election year.