Whatever the mythology, the 2006 election was won for Democrats by moderates running in normally "red" areas. Americans are getting heartily sick of politics in general, and I suspect extremists in either direction aren't going to be all that appealing. We hear a lot of noise about them from the bases on the Left and the Right, because frankly, the bases have the time and energy to make a lot of noise. Most of the rest of Americans have jobs.

I would not be happy at all with Ron Paul as the candidate, and I suspect most of the workers and others who used to be the heart of the Democratic Party wouldn't be all that happy with someone like Kucinich, either.

Hillary can do "moderate" like nobody's business, and most of the top tier of Republicans won't have much trouble with it, either.