Assuming that at that point Barack Obama still holds his lead in elected delegates and in votes cast in the Democratic primaries, Clinton will then have to make up her mind whether to quit right away or to hang on until the August presidential nominating convention. Her one hope would be that a clear majority of the remaining uncommitted "superdelegates" comes off the fence onto her side.
Much more probably, these superdelegates, who range from former vice-president Al Gore to party officials barely known inside their own state, will decide that they should vote as ordinary party members have already done in all the primaries. At that moment, it will be all over for Clinton.
Or so all the political experts take for granted. Most probably, they are right. But they've overlooked one alternative possibility. One way does exist for Clinton to continue to run even after losing the Democratic nomination. She could run as an independent.
Not likely, of course. But not impossible.
This thought first occurred to me while watching a clip of Clinton being interviewed on TV the morning after her Pennsylvania victory.
She was, I realized, totally consumed and utterly obsessed by the contest she's now engaged in.
Political contests do of course send an addictive surge of adrenaline through almost all of those engaged in them. But fighting to become president has become Clinton's entire life, her very reason for existing.
A day later I came upon a blog by an American political commentator, Andrew Sullivan, that eloquently expressed my own thoughts.
Clinton can't win the Democratic nomination, he wrote, "But she won't leave. She will never leave."
Sullivan then gave an analysis of why Clinton won't leave, which went far beyond the standard commentary about her toughness, her determination, her take-no-prisoners style of campaigning.
"Ceding to someone younger is unthinkable to her. It would be a form of death to her," he wrote.
That's rough. But Sullivan has spotted something essential about Clinton. There's something quite out of the ordinary about the magnitude of Clinton's ego, about the scale of her sense of entitlement, about her conviction that the presidency is her birthright.
The chances that Clinton would run as an independent really are remote. She'd be turning her back on the party to which she and Bill have given their lives. Raising funds would be all but impossible.
All Clinton could hope to achieve would be to make certain that Obama lost and that Republican John McCain won.
Except that this is exactly what she's – mostly – now done. Her relentless, ruthless, "kitchen sink" attack on her rival has already significantly damaged Obama.
She has made him look too nicey-nice to be president. As damaging, she's made him look less like a new kind of politician. Any time Obama counterattacks, as he does occasionally and reluctantly, he sounds like an old-style politician, like Clinton herself.
Although Obama may figure out a way to be true to himself while dodging the rocks Clinton keeps hurling at him, she has already to a considerable degree achieved what running as an independent could do for her.
She has ensured that "someone younger," in Sullivan's insightful observation, will not become president in her place. The remote chance that she might still win the Democratic nomination has become an excuse for her to continue fighting – against the kind of hopeful young politician she once was.
As a politician, Clinton is decidedly conventional, except for her professionalism, her competence, her resilience, her ruthlessness.
But as a personality, she's the most interesting character in American public life in ages.
