WASHINGTON — Senator Clinton will return to New York City this evening for the final election night of the Democratic presidential primary, as she faces the likelihood that Senator Obama will secure enough delegates to clinch the nomination soon after the polls close in Montana and South Dakota.

The homecoming announcement by the Clinton campaign set off rampant speculation yesterday that the former first lady would end her White House bid, but a spokesman told reporters late yesterday that Mrs. Clinton had no plans to concede tonight. And at a rally in South Dakota last night, Mrs. Clinton told supporters she would make her case to superdelegates “over the coming days,” suggesting that a departure from the race was not imminent.

Yet amid increasing signs that party leaders are preparing to rally quickly around Mr. Obama, Mrs. Clinton’s top supporters appeared to be coming to grips with the reality that her hopes for victory had evaporated. Her claim to an edge in the overall popular vote gained little visible traction yesterday, as Mr. Obama announced endorsements from another six superdelegates, edging him closer to the 2,118 total now required for the nomination.

“At the end of the day, this is ultimately about delegates, and the math is very hard to argue away,” a longtime friend of the Clintons told The New York Sun yesterday, speaking on the condition of anonymity because he remained committed to her candidacy. “I will be with Senator Clinton until she tells me otherwise.”

Stumping for his wife in South Dakota, President Clinton suggested the end was near. “I want to say also that this may be the last day I’m ever involved in a campaign of this kind,” Mr. Clinton said, according to the Associated Press.

Mr. Obama will hold an election night rally in St. Paul at the site of the Republican National Convention in September, but whether he would be able to declare an outright victory was unclear. He told reporters that he thought he had “a good chance” of reaching the magic number of delegates “between Tuesday and Wednesday.”

He said he had called Mrs. Clinton on Sunday night and broached the idea of a meeting between the two “once the dust settled.” The meeting, he said, would come “at a time and place of her choosing.”

Mr. Obama is scheduled to be in Manhattan tomorrow afternoon for a pair of fund-raisers, and both candidates are scheduled to address the American Israel Public Affairs Committee tomorrow morning in Washington. That event is the last that Mrs. Clinton has on her schedule, and reports yesterday indicated that her field staffers across the country had been told they could either fly home or attend her election night party tonight in New York.

Mrs. Clinton has also invited her top donors to the event tonight, to be held at Baruch College on the East Side.

Uncommitted Democratic lawmakers reportedly met yesterday afternoon on Capitol Hill to plan a group endorsement of the nominee.

One top Democratic House member who had remained neutral, Rep. James Clyburn of South Carolina, confirmed to the AP yesterday that he would endorse Mr. Obama today.

Mr. Obama finished the day with a total of 2,076 delegates and needing 42 to clinch the nomination. Just 31 pledged delegates are at stake in Montana and South Dakota today, meaning the Illinois senator will need additional superdelegates to announce their backing.

Though both candidates have campaigned in each state, the primaries themselves may be an afterthought, given the trajectory of the race. Polls predict Mr. Obama will win Montana easily, but few reliable surveys have been conducted in South Dakota.