Seeing a good possibility that the Democratic presidential nomination will not be settled in the primaries and caucuses, Senators Hillary Rodham Clinton and Barack Obama are lavishing attention on a group that might hold the balance of power: elected officials and party leaders who could decide the outcome at the convention in August.
There are 796 of them, and if neither Mr. Obama nor Mrs. Clinton emerges from the primary season with the 2,025 delegates necessary to secure the nomination, they will in essence serve as tiebreakers. That is a result both sides see as increasingly likely.
Known as superdelegates because they are free to cast their votes at the convention as they see fit, they are the object of an intensifying and potentially high-stakes charm offensive by the candidates and their supporters.
“We have all been bombarded with e-mails from everybody and their mamas,” said Donna Brazile, a senior member of the Democratic National Committee. “Like, ‘Auntie Donna, you’re a superdelegate!’ My niece called me today to lobby me. I didn’t know what to say.”
Mr. Obama, of Illinois, and Mrs. Clinton, of New York, are setting aside hours each week to call superdelegates, and their campaigns have set up boiler rooms to pursue likely targets.
The Clinton campaign has established a system, overseen by one of the party’s most seasoned behind-the-scenes operators, Harold Ickes, to have superdelegates contacted by carefully chosen friends and local supporters, as well as by big-name figures like Madeleine K. Albright, a former secretary of state. For particularly tough sells, the campaign has former President Bill Clinton or Chelsea Clinton make the call.
Mr. Obama has enlisted Tom Daschle, the popular former Senate majority leader, as well as Gov. Janet Napolitano of Arizona and Senator John Kerry of Massachusetts, the party’s 2004 presidential nominee.
“You know there is something interesting going on when you pick up your cellphone and see all those out-of-state phone numbers,” said Representative Gabrielle Giffords of Arizona, who reported getting calls from Ms. Napolitano and Mr. Daschle.
A survey of the superdelegates by The New York Times that was completed a week ago found that 204 had decided to back Mrs. Clinton, 99 backed Mr. Obama and the rest said they were undecided or did not respond. The survey came before the coast-to-coast contests on Tuesday, and the superdelegates can change their minds at any time.
Surveys by other news organizations have shown Mr. Obama in a stronger position, underlining the difficulties facing news organizations — and campaigns — trying to get a firm count from this group of delegates.
The superdelegates include all Democratic governors and members of Congress, as well as officials and other prominent members of the party. In interviews, some said they were grappling with how to use their power if it comes into play, especially if their judgment does not match the will of a majority of voters.
Should they ratify the decision by regular delegates and vote for the candidate who is ahead in June, no matter how small the lead? Are they obligated to follow the vote of their constituents in primaries or caucuses? Or should they simply follow their conscience and vote for whomever they think is the best nominee?
Superdelegates, created in 1982, were intended to restore some of the power over the nomination process to party insiders, tempering the zeal of party activists. About 15 to 20 percent of the delegates at Democratic conventions are superdelegates.
In the close race for the Democratic presidential nomination in 1984, superdelegates overwhelmingly supported Walter F. Mondale, helping to secure his defeat of Gary Hart. This year, the competition is more intense, and the superdelegates’ support more evenly divided.
Mr. Obama, talking to reporters in Seattle on Friday, said he believed superdelegates should follow the will of the voters.
“My strong belief is that if we end up with the most states and the most pledged delegates from the most voters in the country, that it would be problematic for the political insiders to overturn the judgment of the voters,” Mr. Obama said. “I think it is also important for superdelegates to think about who will be in the strongest position to defeat John McCain in November and who will be in the strongest position to ensure that we are broadening the base, bringing people who historically have not gotten involved in politics into the fold.”
Mrs. Clinton, campaigning Saturday in Maine, disputed Mr. Obama’s interpretation of how superdelegates should make their decision, arguing, as her aides have in conversations with superdelegates, that they should make an independent decision based on who they thought would be the strongest candidate and president. She brought up Senators Kerry and Edward M. Kennedy of Massachusetts; both men have endorsed Mr. Obama, but Mrs. Clinton won that state on Tuesday.
“Superdelegates are, by design, supposed to exercise independent judgment,” she said at a news conference in Maine, according to MSNBC. “But, of course, if Senator Obama and his campaign continue to push this position, which is really contrary to what the definition of a superdelegate has historically been, I will look forward to receiving the support of Senator Kennedy and Senator Kerry.”
Chris Redfern, the Ohio Democratic Party chairman, said he did not intend to pledge his vote until after all the primaries were completed. “You want to make the convention interesting, don’t you?” Mr. Redfern asked.
He said Mrs. Clinton and Mr. Obama had sought his support, as a superdelegate and as the head of the Ohio party. Neither offered him any inducements, he said, “not even a T-shirt.”
Democrats, including aides to both candidates and party leaders, said they were concerned about a summer-long fight should the primary voting end in June without a clear winner.
“It is going to be an enormous train wreck unless by June 3 a candidate has a majority,” said Senator Bill Nelson of Florida, who supports Mrs. Clinton. “I don’t think we want to go back to those wheeling-dealing, smoke-filled back-room days.”
The prospect that the nomination could be decided by party insiders rather than by the voters has stirred unease among many superdelegates as they weigh potentially conflicting loyalties to their constituents and to Mrs. Clinton and Mr. Obama.
Several legislators said they would stay neutral as long as possible, hoping to be spared a decision. But, they said, they are prepared to step in and try to push the party to a decision as soon as the voting is over.
“Once the primary season is over, I am hoping we will have a nominee,” said Senator Benjamin L. Cardin of Maryland. “If those of us who are uncommitted can help bring that about, then I think we should try to do that.”
Senator Amy Klobuchar of Minnesota, who is neutral, said she would not stay on the sidelines for long once the voting was over. “I will not go through the summer, I can tell you that, without endorsing a candidate,” she said. “I am not a big believer in smoke-filled rooms.”
Aides to Mrs. Clinton and Mr. Obama said it had been increasingly challenging to lock down supporters as they traded victories in primaries and caucuses.
Under Democratic Party rules for primaries, delegates are allocated proportionately — rather than winner take all — which complicates the candidates’ efforts to build up a big lead.
“The people who were initially inclined to either candidate got on board early,” said Mr. Ickes, a 40-year veteran of Democratic National Committee battles who is running the operation for Mrs. Clinton out of her headquarters in Virginia. “But at this point, it’s getting harder to get people — especially if they now think there is no front-runner.”
Some of Mr. Obama’s supporters signaled they might battle hard to keep any advantage Mrs. Clinton maintained in superdelegates — in part a dividend from the long relationship of the Clintons with the Democratic National Committee and elected officials — from overcoming any advantage Mr. Obama might have in pledged delegates from the primaries and caucuses.
“My personal opinion is it would be a mistake and disastrous either way for the superdelegates — insiders, establishment politicians — to come along and overturn the expressed view of those pledged delegates,” Mr. Kerry said.
Senator Ron Wyden of Oregon said he had not taken sides, partly out of the hope that the fight would not end up on his plate, but also because he needed to work with both candidates in the Senate on health care legislation.
“I want to spend my time doing as much as possible to have this teed up for a Democratic president,” Mr. Wyden said of the health care plan. “That being said, if this goes until the very end, I am going to have to swallow hard and make a judgment.”
John M. Broder contributed reporting from Washington, and Jeff Zeleny from Seattle.