One interesting thing here is that most self-identified Democrats are very happy with the Democratic Party, which is not the impression you would get from reading blogs where folks like me who are to the left of Democratic Party politicians are regularly castigated as crypto-conservatives. The other is simply that people disagree about where the Democrats stand, but everyone sees Republicans and the “tea party movement” about the same.
Now on to the irresponsible speculation. Looking at this chart, I wonder if Republican politicians are benefitting from a psychological anchor phenomenon around the fact that the media has adopted the conceit that there’s something called the “tea party movement” that’s distinct from the conservative base of the Republican Party. Voters seem to see themselves as about equidistant between Democrats and Tea Parties, which means they’re closer to Republicans than to Democrats. But it’s hard for me to think of important policy disputes between, say, John Boehner & Paul Ryan and tea party leaders.
Someone told me at Netroots Nation that in her opinion the group she works for had made a mistake in not diverting some funding away from HCAN and toward single-payer groups precisely in order to create this sort of anchor.