Inversely, I don't think the people who wouldn't vote for a black-woman aren't as "extreme partisan wing"ed as you might think. I heard a lot of people back in 08 that I would never have considered racist, or extremist, tell me they'd "never vote for a woman, just couldn't do it". My observation as an arm-chair amateur psychologist, would be that I think voting for a women still bothers a great deal of men subconsciously. There's probably been documented studies on this I'm sure, but I think subconsciously a lot of men have a problem seeing women in a position of power. I think it's the same reason that female stand-up comedians get heckled notoriously more than their male counterparts. I think a strong case for this could be made with the Sarah Palin/ McCain card of 08'. I thought Palin hurt him, because given the historical circumstance of Obama being the first partially black president, I think McCain would've been better off picking some white-guy. It was still a close race, but I thought he'd probably have done a lot better just running on tradition, or what has always been. Whether it was Palin being a woman, or if it was Palin being a complete dolt, that hurt McCain could be argued, I guess there's no way of really telling.
Ultimately this comes down to simple reasoning for me though, are the majority of people not bigoted? Of course, but, given that the majority of Romney supporters are white, would it not logically behoove him not only from a racial stand-point, but also a historical stand-point, to pick another white-male to be his running-mate?