Jonathan Bernstein expands on this thought:
Rovism is a horrible political strategy for lots of reasons, but fundamentally it just can't work. Oh, one can get elected anyway; political strategy isn't important enough that it can sink all that many candidates. But it is a reason, maybe the reason, that Republicans have been, for a long time, the natural minority party in the United States: they are willing to dismiss large chunks of the population -- of American citizens -- as not real Americans. Not all Republicans, not all the time, but plenty of them, including their leaders, enough of the time.
Sarah Palin is the candidate of those Republicans, the Republicans who either believe in "real America" or are willing to exploit those who do.
Can you imagine Sarah Palin ever saying that there is no red America and no blue America, but just America? Can you imagine her ever discussing her opponents without a sneer?