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I think this chart, from Kevin Drum, shows this. Over the past few decades, America has gone through some really radical changes, but from these charts you'd never realize it because since 1980 or so the liberal/moderate/conservative counts have remained steady. The moral of the story: people don't really care about ideology. They want their problems addressed. And I suspect if you looked at the 30 years prior to this you'll see a similar graph--I remember reading a book about FDR and it said that in 1936, right before Roosevelt won 48 states, 55% of the country considered themselves conservative. Yep, they said that before electing the most liberal president ever in an historic landslide.
So, basically, all this is irrelevant. The question is, as it has always been: where do people stand on the issues?