As a result, there's likely to be no immediate stampede to endorse the Illinois senator by the party's 300 or so undeclared superdelegates - the people who will determine the nominee.
Most of those superdelegates will wait to see what happens in the weeks to come, to see whether Obama can recapture the magic and whether Clinton's financially strapped campaign can raise enough money to continue.
They will try, too, to gauge Obama's ability to stand up to Republican John McCain in the fall, particularly in big swing states, such as Pennsylvania and Ohio, and to assess the seriousness of the doubts on that score raised by Clinton in the last few weeks.
Increasingly, her message has been simple and blunt: I can beat McCain. He can't.
But time is running out for Clinton. And Obama, even in defeat, remains in much the stronger position to win the presidential nomination.
For his campaign, though, the results yesterday had a disturbingly familiar feel to them, raising anew questions about his ability to close the deal with voters.
Two weeks ago, he was gaining ground on Clinton in Pennsylvania and seemed, perhaps, on the way to a knockout victory that would have ended the race.
Then he stumbled, caught up in the flap over his comments about "bitter" small-town Pennsylvanians and slowed by his widely panned performance during the debate in Philadelphia.
So a familiar pattern was repeated.
Once again, the late-deciding voters - those who had enough interest in Obama not to have committed to his rival early on - broke overwhelmingly for Clinton, for her familiarity and her experience.
Twice before, in New Hampshire on Jan. 8 and Texas on March 4, Obama had been in position to put Clinton away and failed. He came up short again last night.
