The race for the Democratic presidential nomination between Senator Clinton and Senator Obama of Illinois is becoming a pitched delegate-by-delegate battle, which is likely to drag out for months and may even be unresolved heading into the Democratic National Convention in Denver in August.

“It is likely that no side will gain an appreciable or significant advantage in overall delegate counts between now and March 4, past March 4, even past April because of the way our party allocates its delegates,” Mrs. Clinton’s communications director, Howard Wolfson, told reporters yesterday. “For all of those who for cycle after cycle wished for a battle that goes to the convention, in terms of neither side definitively wrapping this up, you could be looking at such a contest here.”

Mr. Obama’s campaign manager, David Plouffe, said Tuesday he did not think a convention fight was probable, but accepted that the battle was likely to drag on for months. “If it goes through June, it goes through June,” he said.

Mr. Plouffe said he thinks that the primaries and caucuses will leave either Mrs. Clinton or Mr. Obama with the “upper hand.” Asked what kind of delegate edge that would involve, the Obama aide said, “I think we’ll know it when we see it.”

While the campaigns sounded sanguine about a protracted contest, the Democratic Party chairman, Howard Dean, vowed to oppose any effort to push the nominating battle through the August convention.

“The idea that we can afford to have a big fight at the convention and then win the race in the next eight weeks, I think, is not a good scenario,” Dr. Dean said Tuesday in an interview with a cable outlet, NY1. “I think we will have a nominee sometime in the middle of March or April. But if we don’t, then we’re going to have to get the candidates together and make some kind of an arrangement. Because I don’t think we can afford to have a brokered convention — that would not be good news for either party.”

Mrs. Clintons’ aides said the electoral map is a challenging one for her in the coming weeks. Nebraska, Washington, and Maine hold caucuses this weekend, a selection method that seems so far to have favored Mr. Obama. Primaries are also scheduled in the next week in Louisiana, Maryland, Virginia and the nation’s capital, all jurisdictions home to large numbers of African Americans, who have voted overwhelmingly for the Illinois senator in other states.

“Senator Obama does enjoy some advantages in the contests in the rest of February but not in a way that should permit him to overcome our lead in delegates,” Mr. Wolfson said. There is no obvious relief for the Clinton campaign until March 4, when primaries take place in Vermont, Rhode Island, Texas and Ohio. Aides to the former first lady said she should perform well in the Lone Star state, where 193 delegates are up for grabs, and the Buckeye state, where 141 are on the line.

Assuming no huge surprises in the upcoming primaries and caucuses, Mrs. Clinton’s first real opportunity to deliver a knockout blow to Mr. Obama might not come until April 22, when Pennsylvania allocates 158 delegates.

If there is no clear victor by that point, two thorny issues could begin to overshadow the remainder of the primary schedule. About 796 Democratic National Committee members and current or former elected officials, known as superdelegates, could be in a position to award the nomination to one candidate or the other. In addition, party leaders will have to struggle with the question of whether delegations from Florida and Michigan, who lost all their delegates for defying the national party’s calendar, should be allowed to vote at the convention.

“Every single delegate is going to matter a great deal,” Mr. Wolfson said. “Superdelegates are going to be critically important. The issue as to how we seat delegations in Florida and Michigan will be critically important.”

At the moment in news organization tallies, Mr. Obama narrowly leads Mrs. Clinton in tallies of so-called pledged delegates chosen through the primaries and caucuses, about 840 to 830. However, she holds a lead among superdelegates, roughly 200 to 120. Most such delegates have not publicly declared an allegiance yet.

If the remaining superdelegates break for Mrs. Clinton as the declared ones have, it is possible that she could win the nomination even though Mr. Obama won more delegates in primaries and caucuses. The Illinois senator said yesterday that he believed the party would not defy the voters.

“I think that those superdelegates who are elected officials, party insiders, would have to think long and hard about how they approach the nomination when the people they claim to represent have said, ‘Obama’s our guy,” Mr. Obama told reporters. The senator noted that superdelegates can change their minds at any point. “They’re not locked in.”

So far, Mrs. Clinton has a firm grip on almost all of New York’s 45 superdelegates. At least 41 are publicly backing her, including the state’s entire Democratic Congressional delegation. However, one Democratic National Committee member who recently moved from Georgia, Marianne Spraggins, has given the near-maximum to Mr. Obama and hosted two fund-raisers for him. In addition, a Manhattan labor lawyer and national party official, Ralph Dawson, donated to Mr. Obama. Neither Ms. Spraggins nor Mr. Dawson returned calls seeking comment.

Mrs. Clinton’s campaign expressed no concern yesterday about relying on superdelegate support, at least to keep their numbers up this month. To counter Mr. Obama’s argument about frustrating the will of the people, her campaign plans to press hard to seat the Florida and Michigan delegations, something he has resisted.

In an all-out floor fight, other factors could also come into play, such as the 26 delegates pledged to John Edwards, who dropped out. He could urge them to go one way or the other, but he can’t dictate their choices. It is also possible that delegates or superdelegates eager for a particular vice presidential choice could seek to impose that on the nominee.