Hillary Clinton has always been the woman who doesn't quit. Her supporters testify to her stamina—how at an endless upstate meeting on agriculture subsidies, she asked penetrating questions when everyone else was asleep; how after umpteen drafts of an important policy address, she wrote the thing herself. Then there's her marriage, how after Bill embarrassed her in front of the world, she stuck by him. She thrives by outlasting everyone. The no-good husband and the cloying press corps, the boring pantsuits and the bad campaign food—all these would bring down most candidates. Not Hillary. She waits and works and wins.

Except when she and her husband lose. In their 35 years in public life, Bill and Hillary Clinton's list of Election Day losses is impressively short—a congressional race in 1974, a re-election for Arkansas governor in 1980 and the disastrous midterm elections of 1994. These setbacks brought out the dark side in both Clintons—his moodiness and self-pity, her paranoia and desire for revenge. But the Clintons have also shown a remarkable capacity to learn from their mistakes, to reinvent themselves and live for another day. After Barack Obama's string of 11 straight primary wins, a Clinton comeback seems improbable, but is far from impossible. The remaining days of the race may well be shaped by lessons learned in past moments of electoral despair.