Here's a new way to visualize how much ground we gained in the House
Unless you’ve been living in a cave for the last six weeks, you know that the Democrats won a pretty smashing victory on Election Day, picking up a net 40 seats in the House of Representatives and overperforming most prognosticators’ expectations. You’re probably also aware that the Republican casualties weren’t randomly distributed among their entire caucus, or that Republican losses weren’t tilted toward their loudest-mouthed doofuses and their most incompetent political practitioners. (Granted, Steve King nearly managed to lose, quite an accomplishment given how dark-red his district is. But, for instance, Louie Gohmert’s asparagus managed to escape without any aspersions being cast upon it.)
Instead, the losses were heavily concentrated in the nation’s swing districts, the ones closest to the national political midpoint. Accordingly, the Republicans who lost were disproportionately among the most moderate members of the GOP caucus—not because moderation is more off-putting to voters in swing districts, though.
Elected officials in swing districts tend to be more moderate because they believe it’ll help them get re-elected (and, if multiple political science studies are correct, that's true). Any moderation advantage, however, is small, and as political polarization continues to increase, it becomes even more likely that if you’re in the wrong party in a closely-divided district in a wave year, you’re probably dead regardless of how much you try to distance yourself from your party. (Just as many moderate Democrats found out to their chagrin in, for example, 2010.)
The orderly precision with which a wave strikes swing district representatives down, though, regardless of their voting record and regardless of their skill as a campaigner, is pretty abstract unless you see it depicted visually. So, I’ve tried to create a graphic that shows just that. Try thinking of the House as a coastal town, with some streets lined with oceanfront property and some set further back from the water. With a big enough wave, just about everything in the first few blocks facing the water gets wiped out. Compared with previous decades when there was more ticket-splitting, it just doesn’t matter much anymore whether you’ve tried to build your own durable brand on a solid foundation of moderation or good constituent service or aw-shucks demeanor; the wave simply doesn’t care. The dark blue blocks, mostly in the middle of the chart, are where all the wave damage is: in other words, the seats that the Democrats picked up in 2018.