In 1992, the Clinton campaign came up with a theme song that evoked the message they hoped would turn a 46-year-old obscure Arkansas governor into the president of the United States: "Don't Stop Thinking About Tomorrow" by Fleetwood Mac. Now it's Barack Obama, also age 46, who has the claim on tomorrow, which is where presidential campaigns have almost always been won in this country. Hillary Clinton still has a chance to recover, but she's bucking this history. Although it would crimp his own foundation work, Bill Clinton desperately wants his wife to be president. But he knows "in his bones," as he likes to say in other contexts, that Obama may be his truest heir.

The 16 years since the Clintons grabbed control of the Democratic Party is the same amount of time that elapsed between the death of Franklin D. Roosevelt in 1945 and John F. Kennedy's Inauguration in 1961. It's a longer period than many of us would care to admit. Kennedy operated "in the shadow of FDR," as the historian William E. Leuchtenberg put it, and he updated the New Deal to the New Frontier. But Kennedy's main argument was that "the torch has been passed to a new generation." So it is today, with the aging baby-boom generation—symbolized by the Clintons—under pressure to move aside.

But as John Edwards says (and Obama also knows, from his community-organizing days), the old order never relinquishes power without a fight. "Iowa Nice" is over. The sweet culture of the cornfields that made Hillary's weeklong attacks on Obama in late November one of the dumbest political strategies of recent years is giving way to states with a more bare-knuckle tradition. The question is how rough the Clintons and their wide circle of political operatives will get. A frantic scramble is underway to feed reporters as much negative information about Obama as possible, but it's slim pickings. I've been leaked stories—if you can call them stories—ranging from his failure to leave more of a mark while he was in college (he made up for it in law school) to his failure to hold more hearings as chairman of the Senate Subcommittee on European Affairs. Not being Eurocentric enough for the foreign-policy establishment is hardly going to sink him.

Democrats of all stripes now have a psychic interest in Obama's success. Even if they're not for him, they're proud of him and of themselves for being in his party. They will not appreciate efforts to take him out, which puts the Clinton campaign in an excruciating bind. The harder they hit Obama, the more they reinforce the impression that all their campaign is about is a grubby struggle to keep their power in the Democratic Party. Many Obama voters I spoke with in Iowa like Hillary personally but resent this sense of entitlement. It's as if they're wearing anti-FDR Democratic campaign buttons from 1940 reading: NO THIRD TERM.

The playbook for a Clinton comeback is George W. Bush's from 2000. After being crushed by John McCain in the New Hampshire primary, he stole some of McCain's message and re-fashioned himself as a "reformer with results." Hillary is now arguing that she has "the experience to make change happen." But Obama has figured out a way to parry the no-experience rap. He simply quotes Bill Clinton from 1992, when he ran against incumbent President George H.W. Bush by arguing that real-world experience was more important than long years of government service. Then he pivots to his side of the field—change.

One of the overlooked findings from the Iowa caucus entrance polls is that many Obama voters still considered Hillary Clinton the most electable Democrat. These people might have trusted their own instincts about the Clintons more. Her electability problems couldn't be more plain: to win in November, Democrats must do better with college-educated men and with independents, the two groups where Obama is strongest and Hillary is weakest. Then there's the slight problem of hatred for the Clintons being the only thing the fractious GOP base can agree on this year. Sadly for her supporters, Hillary is indeed as much of a unifier as Obama—but of Republicans.