So why does she keep going?
One theory is psychological, almost Aesopian. Hillary Clinton - like her husband - is a creature who follows her nature. Scorpions must sting. Ants must save food for winter. Clintons must fight.
Bill Clinton illustrated Clinton grit when he confronted Newt Gingrich during the government shutdown of the mid-'90s. "Do you know who I am?" Clinton said to Gingrich. "I'm the big rubber clown doll you had as a kid, and every time you hit it, it bounces back. That's me - the harder you hit me, the faster I come back up.""That was not bravado," writes Commentary's John Podhoretz, author of a book about Hillary Clinton titled "Can She Be Stopped?" "It was a warning, and an accurate one. The Clintons are without shame, and therefore we all believe they are without honor and cannot possibly imagine themselves as heroes. But Bill very much believed, and believes, that he is a hero because he would not allow himself to be defeated, no matter what - and that part of his eventual victory would be that he could use the virulence of his foes to his advantage."
Hillary sees herself the same way. The Clintons have campaigned as a unit. They see themselves as a team. They are fighters.
But they aren't fools. The Clintons know how to mount a tactical retreat. Indeed, Bill's career has been one long jujitsu match in which he's used his enemies' weight against them, falling backward to get the advantage.
So again, why is Hillary staying in?
Perhaps it's the best route to long-term victory. Washington has long swirled with rumors that the Clintons are holding some "nuclear option" in reserve against Barack Obama. The latest theory is that they've decided not to use it, as it would destroy them, too. Who knows what it might be, if it exists at all. But it's worth noting that if Hillary were the take-no-prisoners brawler everyone says she is, she would almost surely have pushed that button by now.
That she hasn't used the doomsday device buried under Clinton HQ might mean it doesn't exist. Or it might mean she's looking beyond 2008.
In her West Virginia victory speech, Hillary emphasized her electability. Obviously, that's now her best argument for persuading the superdelegates. But it's an even better argument for positioning herself as the "I told you so" candidate after an Obama defeat.
Just because the Clintons say something doesn't mean it's untrue. Hillary's claim that she would do better against John McCain in swing states such as West Virginia - no Democrat has captured the White House without winning there since 1916 - is quite plausible. Obama is in danger of being cast as the Michael Dukakis of the 21st century (fairly or not). Polls show that in West Virginia, Obama wins only 53 percent of Democratic primary voters in a matchup against McCain. When only half of the party base is willing to vote for the nominee against a Republican, that nominee and that party have real problems.
If Obama does implode, Hillary's bitter-end fight would position her to say to Democrats, "You were warned."
Obviously, she wants to win this year. But the conventional wisdom that she's hurting herself within the party by not bowing out gracefully might be flawed. Polls show that Democratic voters want the race to continue. And so long as she can avoid blame for Obama's loss, she'll be in great shape for 2012. She will be able to argue that Democrats must think with their heads, not their hearts, if they want to win the presidency and change the country. Her centrism would no longer seem calculated. And, of course, the identity-politics bean counters will argue that, this time, it really is a woman's turn.
Hillary will do all she can to appear supportive of Obama should he get the nomination. But appearances can be deceiving. Clinton biographer Carl Bernstein recently reported on the Huffington Post that Sidney Blumenthal, the Clintons' preferred smear artist and rumor spreader, has been pushing the press to cover Obama's ties to Bill Ayers, an alum of the left-wing terrorist group the Weather Underground, as well as "many other questionable allegations about Obama."
The real test of my theory will be whether the Blumenthal operation shuts down after the Clinton campaign does.