If Hillary Clinton wanted a graceful exit, she'd drop out now—before the March 4 Texas and Ohio primaries—and endorse Barack Obama. This would be terrible for people like me who have been dreaming of a brokered convention for decades. For selfish reasons, I want the story to stay compelling for as long as possible, which means I'm hoping for a battle into June for every last delegate and a bloody floor fight in late August in Denver. But to withdraw this week would be the best thing imaginable for Hillary's political career. She won't, of course, and for reasons that help explain why she's in so much trouble in the first place.

Withdrawing would be stupid if Hillary had a reasonable chance to win the nomination, but she doesn't. To win, she would have to do more than reverse the tide in Texas and Ohio, where polls show Obama already even or closing fast. She would have to hold off his surge, then establish her own powerful momentum within three or four days. Without a victory of 20 points or more in both states, the delegate math is forbidding. In Pennsylvania, which votes on April 22, the Clinton campaign did not even file full delegate slates. That's how sure they were of putting Obama away on Super Tuesday.

The much-ballyhooed race for superdelegates is now nearly irrelevant. Some will be needed in Denver to put Obama over the top, just as Walter Mondale had to round up a couple dozen in 1984. But these party leaders won't determine the result. At the Austin, Texas, debate last week, Hillary agreed that the process would "sort itself out" so that the will of the people would not be reversed by superdelegates. Obama has a commanding 159 lead in pledged delegates and a lead of 925,000 in the popular vote (excluding Michigan and Florida, where neither campaigned). Closing that gap would require Hillary to win all the remaining contests by crushing margins. Any takers on her chances of doing so in, say, Mississippi and North Carolina, where African-Americans play a big role?

The pundit class hasn't been quicker to point all this out because of what happened in New Hampshire. A lot of us looked foolish by all but writing Hillary off when she lost the Iowa caucuses. As we should have known, stuff happens in politics. But that was early. The stuff that would have to happen now would be on a different order of magnitude. It's time to stop overlearning the lesson of New Hampshire.

Hillary has only one shot—for Obama to trip up so badly that he disqualifies himself. Nothing in the last 14 months suggests he will. He has made plenty of small mistakes, but we're past the point where a "likable enough" comment will turn the tide. When Obama bragged in the Austin debate about how "good" his speeches were, the boast barely registered. He has brought up his game so sharply that even a head cold and losing the health-care portion of the debate on points did nothing to derail him. Hillary's Hail Mary pass—that Obama is a plagiarist—was incomplete.

So if the Clintonites were assessing with a cold eye, they would know that the odds of Hillary's looking bad on March 4 are high. Even Bill Clinton said last week that Texas and Ohio are must-win states. If she wants to stay in anyway, one way to go is to play through to June so as to give as many people as possible a chance to express their support. While this would be contrary to the long-stated wish of many Democrats (including the Clintons) to avoid a long, divisive primary season, it's perfectly defensible.