Ambers largely blames political polarization in the House on redistricting:
[U]ltimately, both the Democratic and Republican parties are responsible for the strategy that has so polarized this chamber of Congress in the first place. Redistricting is controlled by state legislatures, and the same Republicans who are now grumbling that the House GOP is throwing away the baby with the bath water were the ones who encouraged conservative donors to focus on state legislative chambers and on electing politicians who were keen to redraw districts in ways that corralled conservative constituencies.
He later notes that "the idea that partisan redistricting alone is responsible for the make-up of the House Republican conference is ridiculous." Ideology matters. The combination of greater ideological coherence and redistricting is a very nasty combo. It can also feed on itself, as Harry Enten argues and new research shows:
Anyway you put it, Democrats and Republican legislators have greater ideological differences than ever. Gerrymandering probably doesn't help, yet it's not the major cause of the problem. Natural geographic divisions on the state and local level between Democrats and Republicans are a big cause in this growing polarization. Both of these, though, fail to account for the fact that even when controlling for district partisanship, there are increasing ideological differences between Democrats and Republicans in Congress.
Sam Wang models the effect of gerrymandering in the last election, focusing on disenfranchised voters:
[T]he disenfranchisement due to partisan-controlled redistricting was a total of 4.4 million voters from both parties. Democrats were disenfranchised more than Republicans, at a ratio of 10:1.
(Chart on political polarization in the House from Voteview.com)