Could Senator Clinton win the Democratic presidential nomination at the last minute by taking advantage of buyer’s remorse among Democratic super-delegates who are dismayed by the performance of Senator Obama’s campaign so far?

Here’s the scenario: Senator Obama has raised tens of millions more dollars than Senator McCain, which Democrats think should translate into an advantage in the polls. The economy is doing poorly, which Democrats think should translate into an advantage in the polls given that the Republicans control the White House and the incumbent party is often blamed for a bad economy.

The Republican nominee-in-waiting, Senator McCain, is old and is unpopular with his party’s base because he has broken with conservatives on taxes, global warming, torture, and campaign speech limitations. The Democrats think that should translate into an advantage for them at the polls, too, even though their presumptive nominee is several kiloparsecs to the left of Mr. McCain.

The Republican incumbent in the White House, President Bush, is personally unpopular, blamed for the Iraq War (as Robert L. Bartley liked to say: “They’ll forgive you for being wrong. What they won’t forgive you for is being right”). Three of the top 15 books on the New York Times bestseller list are Bush-bashing tomes; one advocates that he be prosecuted for murder. The Democrats think that this, too, should translate into an advantage for them at the polls.

Despite all these factors, Mr. McCain is running roughly even in the polls with the presumptive Democratic nominee, Mr. Obama, a time when he is supposed to be way ahead. In early August of 1988, Governor Dukakis was ahead of Vice President Bush by a wide margin. In early August of 2004, Senator Kerry was ahead of President Bush. If Mr. Obama doesn’t have a big lead now, it could get pretty ugly for the Democrats as November approaches, the theory goes.

It will only get worse when Messrs. McCain and Obama face off in presidential debates. The public will discover that Mr. Obama, notwithstanding his reputation as a silver-tongued orator, is not that good a debater — which explains why he did his best to dodge debate invitations from Mrs. Clinton and Mr. McCain. Feature Mr. Obama’s flubbering on the outbreak of war between Russia and Georgia.

Is all this enough to prompt Democratic super-delegates to re-think their allegiance to Mr. Obama and hand the nomination to Senator Clinton? If you count Michigan, Mrs. Clinton won the reported popular vote in the Democratic primaries and caucuses, 17.8 million to 17.5 million, and won many of the hotly contested big battleground states that the Democrats need to win in November — Pennsylvania, Ohio, California, New York, New Jersey, Florida. She won Massachusetts even after Senators Kennedy and Kerry endorsed Mr. Obama.

Take away the delegates Mr. Obama has by virtue of the endorsement of Senator Edwards, who has newly admitted deceiving the electorate about the adultery he committed while his wife lay stricken with cancer, and the delegate gap is even narrower. Even Mr. Obama doesn’t have enough delegates to win the nomination without the super-delegates, so there wouldn’t be anything terribly exceptional about the super-delegates putting her rather than him over the top.

Probably all this isn’t enough — at least not yet. But what if, by the time the convention rolls around, Mr. Obama isn’t just running neck and neck with Mr. McCain but is lagging by, say, five percentage points, or if Mr. Obama makes a big blunder with his choice of a running mate, or some other campaign stumble? Then expect the whispers already swirling among Clinton supporters to turn into a full-fledged roar.

Mrs. Clinton’s Tuesday keynote address, scheduled for the Tuesday of the Convention, could then start to sound less like an endorsement speech and more like a final campaign plea. If it’s a real hit, anything can happen. Expect, too, the well-timed release of some public poll showing Mrs. Clinton doing better than Mr. Obama in matchups against Mr. McCain in battleground states. Already the Clinton campaign is surfacing, through the forthcoming issue of the Atlantic Monthly, a memo portraying Mr. Obama as “not at his center fundamentally American in his thinking and in his values.”

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This newspaper doesn’t presume to tell the Democrats whom to nominate, but we did start out this campaign hoping for three New York presidential candidates. Mayors Giuliani and Bloomberg are out of the race for the top spot on any ticket, though Mr. Bloomberg may still prove attractive as a vice presidential candidate. We have no illusions about the ultra-long-shot of Mrs. Clinton’s chances of actually emerging as the Democratic nominee, but they are not technically impossible, as Mr. Obama is no doubt aware. Mr. Obama skipped a visit to a military hospital in Germany. He spent this weekend on vacation in Hawaii. Mrs. Clinton spent last week visiting wounded service members at Fort Drum. Mr. Obama may think the primary campaign is over, but Mrs. Clinton’s die-hard supporters still itch for a last-minute surprise.