How do you know?

People ask that all the time. How do you know when you're in love? How do you know when you're not in love? How do you know when it's over?

The answer is always the same. You know when you know. If you have to ask, the answer is, not yet.

That's the answer to the question of whether the Democratic race is over.

Not yet.

Races end when a candidate puts down his hand, or her hand, or when the people who would never endorse while there was still a contest endorse, when all the money is flowing in one direction, and the only question is when and not if.

That is, plainly, what is happening on the Republican side. The first President Bush is endorsing. All the former candidates have endorsed. The arithmetic works only one way. The fat lady is singing, whether former Governor Huckabee chooses to listen or not.

The Democratic side is another story. Has Obama got momentum? Yes. But this is a race that has been curiously immune to moment, and downright perverse when it comes to predictions.

Could Hillary still win? She could. The delegate count as of the weekend stood at 1280 for Obama and 1218 for Clinton. By most people's logic, that looks like a tie. Add in Florida and Michigan, and one way or another, there will be delegates from those states at the National Convention, and Hillary is actually ahead. So how can it be over?

Once you declare a firewall, it needs to hold. Hillary has named the Big Three. She has to win Ohio, Texas and Pennsylvania – and win them in a commanding enough way to give her credibility with the still-unpledged superdelegates and spread some doubt among opinionmakers and media types who are itching to crown Obama.

IF she does that, and, of course, that's an "if," the rest is doable. The battle for superdelegates is the kind of fight the Clintons excel at — not only because Bill Clinton may be the hardest man in the world to say no to (politically, I mean), but also because this is where 35 years of favors and chicken dinners and contributions get paid off.

Sure, loyalty won't lead many people to back a loser. If Hillary loses Ohio, Texas and Pennsylvania, all the rubber chicken in the world won't bring her the votes of the people who have to run with her in the fall. But so long as the contest is as even as it is now, there will be plenty of Clinton people arguing that the lesser-known candidate is a bigger risk than the better-known one, that experience is what it takes to take on John McCain, and yes, that debts must be paid.

The fact that Harold Ickes, Hillary's chief delegate counter and one of the Democratic Party's long-time rules junkies (he got me hooked back in 1980), has now changed his tune on seating delegations from Florida and Michigan should tell you how the Clinton people see this playing out. One way or another, every state ends up with delegates on the floor, no matter what the party threatens in advance.

The question is how they get there, or in this case, according to what vote they get apportioned. The Clinton people will argue that the only fair thing is to apportion them based on the votes that were actually cast in the admittedly verboten primaries. The Obama people, who are specialists in caucuses, will argue that they should be picked by the state parties, or by caucuses, or by some other procedure that Hillary hasn't already won.

Who wins? Believe me, this isn't a question of principle. It's all politics, and it will depend both on how well Hillary does between now and then, and on how much support she has on the Democratic National Committee.

Technically, the decision could be made in the first instance by the DNC, and then challenged (or affirmed) by the Credentials Committee to the Convention, and the Convention itself.

The composition of the Credentials committee is based on the division of pledged delegates to the convention, which doesn't tell you anything yet, and if it's left to the convention reviewing the Credential Report, then it's pledged delegates plus superdelegates minus the Michigan and Florida delegations, who don't get to vote on their own challenges. Which is to say, again, who knows?

Whoever wins, wins. That's how politics works. But no one has won yet.

Stay tuned. Believe me, this kind of race is much more fun to watch than to wage. More sleep, too.

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Susan Estrich is the Robert Kingsley Professor of Law and Political Science at the University of Southern California. She was Professor of Law at Harvard Law School and the first woman President of the Harvard Law Review. She is a columnist for Creators Syndicate and has written for USA Today and the Los Angeles Times.

Estrich's books include the just published “Soulless,” “The Case for Hillary Clinton,” “How to Get Into Law School,” “Sex & Power,” “Real Rape,” “Getting Away with Murder: How Politics Is Destroying the Criminal Justice System” and "Making the Case for Yourself: A Diet Book for Smart Women.”

She served as campaign manager for Michael Dukakis' presidential bid, becoming the first woman to head a U.S. presidential campaign. Estrich appears regularly on the FOX News Channel, in addition to writing the “Blue Streak” column for FOXNews.com.

Susan Estrich is currently the Robert Kingsley Professor of Law and Political Science at the University of Southern California and a member of the Board of Contributors of USA Today. She writes the "Portia" column for American Lawyer Media and is a contributing editor of The Los Angeles Times. She was appointed by the president to serve on the National Holocaust Council and by the mayor of the City of Los Angeles to serve on that city's Ethics Commission.

A woman of firsts, she was the first woman president of the Harvard Law Review and the first woman to head a national presidential campaign (Dukakis). Estrich is committed to paving the way for women to assume positions of leadership.

Books by Estrich include "Real Rape," "Getting Away with Murder: How Politics is Destroying the Criminal Justice System" and "Dealing with Dangerous Offenders." Her book "Making the Case for Yourself: A Diet Book for Smart Women," is a departure from her other works, encouraging women to take care of themselves by engaging the mind to fight for a healthy body. Her latest book, The Los Angeles Times bestseller, "Sex & Power," takes an impassioned look at the division of power between men and women in the American workforce, proving that the idea of gender equality is still just an idea.