A SPECULATIVE HYPOTHESIS
It's interesting to watch Sarah Palin being viciously and gleefully mocked by Sarah Bernhardt, Julie Brown, Saturday Night Live, David Letterman, Garry Trudeau, and so many others in a kind of piling on. She's attacked for her look, background, accent, and culture-- in a way that would never be done to a minority candidate. It's a visceral, undisguised hatred of the white lower-middle class. By contrast Obama is treated by white liberals as one of them.
The white liberal culturati based on their islands of privilege don't see themselves as white Americans-- they're "Citizens of the World"-- ironically enough, as THEY were the beneficiaries of America's racism, and not the gun-toting hard-scrabble citiziens of places like western Pennsylvania, many whose families worked in coal mines, or of Alaska, for that matter. It's because of this very guilt that liberal minds disconnect themselves from their own heritage.
Sarah Palin is everything they hate, in part because she clings to the ideals of America past-- and it must be said that much of affluent liberal hate is self-hate.