So, as I said, the parties now live in different universes, both intellectually and morally. We can ask how that happened; there, too, the parties live in different worlds. Republicans would say that it’s because Democrats have moved sharply left: a Republican National Committee fund-raising plan acquired by Politico suggests motivating donors by promising to “save the country from trending toward socialism.” I’d say that it’s because Republicans have moved hard to the right, furiously rejecting ideas they used to support. Indeed, the Obama health care plan strongly resembles past G.O.P. plans. But again, I don’t live in their universe.

More important, however, what are the implications of this total divergence in views?

The answer, of course, is that bipartisanship is now a foolish dream. How can the parties agree on policy when they have utterly different visions of how the economy works, when one party feels for the unemployed, while the other weeps over affluent victims of the “death tax”?

Which brings us to the central political issue right now: health care reform.