For instance, Obama gets called a tax-raising, re-regulating socialist all the time. There are some Republicans who actually believe this, but I think that the folks who broadcast this stuff know that Obama will lean right to prove them wrong. He's cut taxes, bailed out banks, and signed fewer regulations into law than any president in recent decades. It's like the guy who starts fights to prove that he's macho, not gay.
I'd argue that Romney chose Ryan as his running mate as part of disproving critics that claim he's more moderate than conservative. After bearing right during the primary (a common and necessary strategy to win votes in the Republican primary), one might have expected Romney to veer back to the center in the general election (again, a fairly common and seemingly necessary strategy). But Romney is going to prove his critics wrong when they label him a flip-flopper, liable to change positions for convenience and votes. So if anything, he seems to be heading further right. (Note the most recent cut all funding to the arts comment he's made.) He's not exactly getting more votes from the center with his talk of medicare cuts either.
The question is whether his commitment to prove his critics wrong will cost him the election.