In fact, as the chart below details, Republican Senate candidates under-performed GOP presidential nominee Mitt Romney in most of the important races of 2012.
In five races, the GOP candidate under-performed Romney by at least nine points. This includes Reps. Denny Rehberg (R-Mont.) and Rick Berg (R-N.D.), who both lost in states that Romney carried by at least 13 points.
In New Hampshire we didn’t have any senate races, but the same phenomenon was observable downticket, including for both GOP House seats. Statewide, Charlie Bass, who’s a classic RINO squish, and Frank Guinta, who isn’t, drew about six per cent fewer votes than Mitt, and both lost. Regardless of what kind of Republican you are, the electorate was antipathetic to you.
In other words, whatever the weaknesses of a supposedly weak candidate, the party was weaker. With hindsight, that first debate performance appears to have made Mitt sufficiently likeable for a narrow slice of voters to overlook the R after his name. The candidate was less of a problem than the Republican brand.