We can also say the following:
Being an incumbent helps. A lot.
Shocking, right? The remarkable electoral ability of incumbent elected officials continues to be demonstrated. In each of the last four cycles, the people winning House seats have overwhelmingly been incumbents -- waves and bad approval ratings aside.
What's more, incumbents continue to win by wider margins than non-incumbents. In 2014, incumbents that won reelection (which is the vast majority of them) won by about 40 points on average, regardless of party. New Republican winners won by 18 points on average; new Democrats by almost 25. (This is according to AP margins in most states and California's latest data.)
There aren't very many close races.
In every cycle, for both incumbents and non-incumbents, victors usually win by at least 10 points. We could predict that most elections wouldn't be close even right afterward, but -- particularly on the Republican side -- it's now obvious.
Compare the GOP incumbent bars on that graph (to the left in each set) from 2012 and 2014. In 2012, when Democrats did much better, GOP incumbents had a much wider distribution of margins of victory. This year, they won more overwhelmingly across the board.
If we look just at how each party did in its margins of victory each year, you can see 1) that most races are won by 10 points or more, and 2) Republicans had a remarkably low number of victories that were in the single digits -- 17 to be exact. That's the lowest number of similarly close races for either party in any of the last four cycles.
It's in those close races that things get interesting, of course -- like the razor-thin Democratic wins in California's 7th and 16th congressional districts. But those happen so rarely that it's no wonder people glaze over.
And even in those races, we'll note, both of the incumbents won.