As potential first spouses, Obama has Michelle, an elegantly beautiful woman who would be the Jackie Kennedy of her husband's new media-conjured Camelot, while Edwards has Elizabeth, a combative cancer survivor. Hillary has Bill, a former president prickly about his legacy who will surely be tempted to try to make her presidency all about his vindication.

George W. Bush's presidency was made more psychologically complex by the fact that his father, George H.W. Bush, was one of his predecessors. Imagine if W. had had to try to run the government together with H.W. "Oedipal city," as his dad might have put it. A Hillary administration promises all that fraught emotional tension and more.

Even now, no one can quite figure out whether Bill is trying to sabotage her with his off-message bloopers, or is vesting everything in her victory as the ultimate vindication of self. What will his role be in her administration, how will it change with the vagaries of their marriage, and who will be right when they say conflicting things about policy?

Who knows, and who can blame anyone for wanting to think about something else? Clintonism delivered the White House to the Democrats twice in campaigns in 1992 and 1996 that hewed to the middle and made the party more appealing than it had been in decades. But no one else has picked up the mantle nationally.

Al Gore would have been the natural ideological successor in 2000, but angered by Bill's spectacularly irresponsible conduct in office, he distanced himself and lurched left. Since the left-wing base of the Democratic Party never liked the Clinton pragmatism, the only ones with support in the party strong enough to maintain a relative centrism are the Clintons themselves.

And so the devil's bargain: Clintonism comes only with the Clintons attached.