Quite simply, not voting for whomever is the nominee is, objectively, a vote for Obama.
I understand your point, but an individual American has to vote as an individual. Supporting, endorsing, Bishop Romney is something that many Americans cannot do, even if they have been voting for Republican candidates for decades.
It is easy to think in terms of Obama versus Romney, but for millions of us, we will not be forced into voting for Romney, no matter how you phrase it, there is a conservative force within the GOP which is fighting to defeat the left, and that fight includes stopping the Romney/Rockefeller element from defeating the Reagan/Palin branch of the GOP.
Where was your argument when you guys were fighting to defeat the GOP Senate candidate in Alaska?