WASHINGTON – Hillary Rodham Clinton retains her lead among suddenly critical Democratic Party insiders even as Barack Obama builds up his delegate margin with primary and caucus victories across the country, according to a survey by The Associated Press.

Of the 796 lawmakers, governors and party officials who are Democratic superdelegates, Clinton had 243 and Obama had 156. That edge was responsible for Clinton’s overall advantage in the pursuit of delegates to secure the party’s nomination for president. According to the AP’s latest tally, Clinton has 1,135 total delegates and Obama has 1,106, with three delegates still to be awarded from Sunday’s Democratic caucuses in Maine. A candidate must get 2,025 delegates to capture the nomination.

The numbers illustrate not only the remarkable proximity of the two candidates, but also the extraordinary influence superdelegates could wield in determining who becomes the nominee. Both campaigns are aggressively pursuing superdelegates, trumpeting their endorsements the moment they are secured.

“I told my wife I’m probably going to be pretty popular for a couple months,” Richard Ray, a superdelegate and president of the Georgia chapter of the AFL-CIO, said with a chuckle. Ray said he would remain undecided because the labor federation has made no endorsement.

“If they endorse, then I will, too,” Ray said.

The national party has named about 720 of the 796 superdelegates. The remainder will be chosen at state party conventions in the spring and summer. AP reporters have interviewed 95 percent of the named delegates, with the most recent round of interviews taking place last week, after Super Tuesday.

For the first time since the AP began contacting superdelegates last fall, more than half of them – 399 – have endorsed a candidate. The remaining 320 or so delegates said they are either undecided or uncommitted, making them the subject of intense lobbying by both campaigns.

With Clinton and Obama trading wins and losses as the primary and caucus season unfolds, the role of the superdelegates has been magnified and is causing anxiety inside and outside the campaigns. If the current snapshot of the race holds, superdelegates could decide the nomination in favor of one candidate even if the other receives more votes in the party primaries and caucuses.

Donna Brazile, a top Democratic National Committee member and manager of Al Gore’s 2000 presidential campaign, said party elders have a role to play but said voters should lead the way.

“I don’t want to superimpose my personal views; I want to reflect the will of the voters,” she said Sunday, noting that as a superdelegate she is torn between Obama and Clinton. “Honestly, I don’t want to decide this.”

Obama himself weighed in Friday, telling reporters that voters should determine whom superdelegates support, even as his campaign actively courted them.

“My strong belief is that if we end up with the most states and the most pledged delegates, and the most voters in the country, then it would be problematic for political insiders to overturn the judgment of the voters,” he said. “I think that should be the guiding approach to determining who will be the nominee.”

Clinton, speaking to reporters on Saturday, argued that superdelegates should make up their own minds and pointedly noted that Obama has the endorsements of superdelegates John Kerry and Edward Kennedy, both senators from Massachusetts, a state whose primary Clinton won.

“Superdelegates are by design supposed to exercise independent judgment,” she said. “If Senator Obama and his campaign continue to push this position, which is to the contrary of what the definition of superdelegates has historically been, I will look forward to receiving the support of Senator Kerry and Senator Kennedy.”

Unlike pledged delegates secured through a primary or a caucus, superdelegates can vote for whomever they choose, and they are not required to vote for the candidate they endorse. Indeed, some superdelegates who had endorsed other Democratic candidates already have switched to Clinton or Obama or are reconsidering their earlier choices.

Democratic superdelegate Christine “Roz” Samuels of Montclair, N.J., said she backed off her preference for Clinton after hearing former President Bill Clinton scoff at Obama’s stance on the Iraq war.

“I’m disappointed in a few things that were said a few weeks ago by President Clinton,” she said. “I’m going to have to revisit what I’m going to do between now and when we vote.”

The Democratic Party introduced superdelegates to the nominating process after the 1980 election with the idea of giving a voice to elected officials and party elders who had a stake in who became the party’s standard-bearer. In 1984, Walter Mondale relied on superdelegates to distance himself from rival Gary Hart and secure the Democratic nomination. Mondale went on to lose to Ronald Reagan in the general election. Since then, the primaries and caucuses have determined the party’s nominee without superdelegates making a difference.

As Democratic senators, both Clinton and Obama are superdelegates.

They now make up about 19 percent of the overall delegates. Obama and Clinton have vigorously lobbied them. Clinton has relied on her best surrogates, not the least of whom is President Clinton. Former Senate Democratic Leader Tom Daschle of South Dakota, who is co-chair of Obama’s campaign, said he spends much of his time calling superdelegates and urging them to vote for Obama. “It could make the difference” for the nomination, he told South Dakota Public Broadcasting.

While the number of new commitments is growing, many superdelegates are still a hard sell.

“I truly am torn. We have two wonderful candidates,” said Steve Achelpohl, chairman of the Nebraska Democratic Party and a superdelegate. Clinton “has a backbone of steel,” he said, and can reach across the aisle to get things done.

Obama is “the instrument of change.”

“He’s rallying our young people in a way that I’ve not seen in my lifetime,” Achelpohl said. “He’s a phenomenon. He’s the next Jack Kennedy.”

Associated Press writers Christine Simmons, Beth Fouhy, Charles Babington, Jeffrey Gold and Shannon McCaffrey contributed to this report.