TROY, Mich. — On the eve of the final two primaries of a five-month marathon, Sen. Barack Obama stood poised to wrap up the Democratic presidential nomination, while Sen. Hillary Clinton weighed whether to stay in the race in hopes of delaying what appears an inevitable outcome.

Obama is optimistic that he will be able to claim victory tonight at a rally in St. Paul, Minn., with superdelegates preparing to rally to his candidacy on the eve of the day's contests in South Dakota and Montana and push him past the threshold of 2,118 delegates needed to clinch the nomination.

Clinton sent mixed signals about her plans throughout the day yesterday. As her campaign recalled field staffers to New York, one adviser indicated that she would suspend, but not end, her campaign within days. But the candidate herself said she would continue to argue to the group of party insiders who will hold sway over the final outcome that her strong showing in recent contests demonstrates that she would be the more electable candidate in November.

"Tomorrow is the last day of the primaries and the beginning of a new phase in the campaign," Clinton said in Yankton, S.D., before she prepared to depart for a rally tonight in New York. "After South Dakota and Montana vote, I will lead in the popular vote and Sen. Obama will lead in the delegate count. The voters will have voted, and so the decision will fall to the delegates empowered to vote at the Democratic convention. I will be spending the coming days making my case to those delegates."

LIMITING THE DAMAGE

Party leaders worked behind the scenes to establish an outcome that would limit the long-term damage from the protracted and divisive campaign, hoping to provide a quick and graceful exit for Clinton and clear the path for the first black presidential nominee.

On Capitol Hill, three uncommitted senators, Tom Harkin of Iowa, Thomas R. Carper of Delaware and Ken Salazar of Colorado, met yesterday to discuss a "quick conclusion" to the Democratic race but were privately urged by Senate Majority Leader Harry M. Reid of Nevada to delay any announcement until the final votes have been counted, according to Democratic sources.

But prominent Democrats predicted that members of Congress would unite around Obama's candidacy before week's end.

Campaigning yesterday in Michigan, a key November battleground, Obama said he considers Clinton a valued ally in his general-election contest against Sen. John McCain of Arizona. Clinton ran "an outstanding race," Obama told a packed crowd in this middle-class suburb of Detroit. He vowed, "She and I will ... be working together in November."

At a later stop in Waterford, Obama recounted for reporters a telephone conversation he had with Clinton on Sunday congratulating her for winning the Puerto Rico primary. He said he told Clinton that "once the dust settled I was looking forward to meeting her at a time and place of her choosing" to talk about the campaign's next phase.

CLINTON'S OPTIONS

As Clinton made a final push for votes across South Dakota, her advisers said her options ranged from dropping out tonight and endorsing Obama to making a final effort to convince uncommitted superdelegates that she would be a stronger rival to McCain.

Another, according to senior Clinton advisers, is what they dubbed the "middle option," for Clinton to suspend her campaign, acknowledging that Obama has crossed the delegate threshold but keeping her options open until the convention in late August.

Clinton has been angered by recent calls for her to quit, her advisers said, and the "soft landing" of suspending her campaign would allow her to move ahead on her own terms.

Speaking to reporters in Sioux Falls, spokesman Mo Elleithee was unequivocal, saying that Clinton intends to spend the next several days "making the case to undecided delegates" and adding: "She's in this race until we have a nominee. She expects to be that nominee."

Former President Bill Clinton sounded wistful before an audience in Milbank, S.D.

"This may be the last day I'm ever involved in a campaign of this kind," he said. "I thought I was out of politics, till Hillary decided to run.

"But it has been one of the greatest honors of my life to go around and campaign for her for president."

FINISH LINE IN SIGHT

Obama campaign officials, meanwhile, held out hope that he would be able to cross the finish line when the polls close in Montana tonight, and that superdelegates would then be ready to come forward in large numbers.

The senator from Illinois expects to pick up around 20 pledged delegates in today's primaries, leaving him roughly two dozen superdelegates short of the 2,118 mark. Sen. Claire McCaskill of Missouri, an Obama supporter, said yesterday that she had spoken to 10 undeclared superdelegates since Sunday and said they all understood that the race was likely to be over tonight.

"They think this competition is about to wind down," McCaskill said. "Yes, they will be committing, and yes, they will be committing before sunset tomorrow."

One advantage to a wave of superdelegates moving to Obama early today is that it would allow him to clinch the nomination with the pledged delegates awarded through voting in the evening as opposed to relying on the support of superdelegates, who are largely elected officials and party insiders.

If not today, Obama aides are confident that the nomination will be secured tomorrow or Thursday, as party leaders begin to close ranks around Obama. Reid, House Speaker Nancy Pelosi and Democratic Party Chairman Howard Dean have all urged a speedy end to the contest once voting is concluded, and many of their colleagues expect them to lead the way in preventing a prolonged standoff.

"There are a lot of superdelegates who are waiting for the last couple of contests, but I think that they are going to be making decisions fairly quickly after that," Obama told reporters in Waterford. "My sense is that between Tuesday and Wednesday, that we've got a good chance of getting the number that we need to win the nomination."