Yeah, this is underrated as a factor on why the House is such trouble for Dems. Gerrymandering is a huge part, but even without that they'd still be in the hole due to the decimation of the Blue Dogs and their inability to break through in many suburban districts that are friendly to them on the presidential level.
2014 was an almost total wipeout for Democrats in heavily Republican areas. Out of all the seats more Republican than R+1, only 4 Democrats won. Democratic incumbents were re-elected in an R+3 and R+6, and strangely there were 2 pickups in R+4s. And R+1s voted for Obama, so those are the only Romney district Democrats.
