PoliPundit offers a useful analysis of why the House went overwhelmingly for the GOP but Senate gains lagged: The House races were largely fought on Republican-leaning turf, but the key Senate fights were in deep-blue states.
That’s true, as far as it goes. But these were, by and large, unpopular incumbent Democrats, often with job-approval ratings in the 40s and disapproval above 50.
Barbara Boxer’s job approval is pretty miserable, underwater by a considerable margin. Harry Reid’s is even worse. Ditto for Michael Bennet in Colorado. Patty Murray was underwater, too. And clearly, Republican wins in blue states were quite possible this year; look at Pat Toomey, Ron Johnson, and Mark Kirk.