Romney, by virtue of his lack of contrast with 0bama, is probably the weakest GOP candidate who could be nominated in 2012. The resultant de-energizing which would consequently occur within the TEA party base would be a critical factor in the general election, quite possibly tipping the situation in 0bama's favor.
Obama = 1/2 White, 1/2 Black, and a member of the DIMS.
About the only differences in my mind.