WASHINGTON (CNN) -- Sen. Hillary Clinton's superdelegate lead over Sen. Barack Obama was narrowed even more Saturday, according to CNN's latest delegate estimate.
Obama closed to within one superdelegate of Clinton, picking up the support of four party leaders after a flurry of new endorsements over the past two days. Clinton, meanwhile, picked up the votes of two superdelegates but lost one to Obama.
That brings Clinton's superdelegate total to 273 and Obama's to 272.
At the beginning of the year, Clinton led the superdelegate race by more than 100.
Superdelegates are Democratic officials who hold the balance of power in determining the party's presidential nominee.
Obama holds a commanding lead in the number of pledged delegates awarded from primaries and caucuses: 1,592 to Clinton's 1,424.
Since Friday night, Obama has picked up four superdelegates, including Arizona congressman Harry Mitchell and Carol Burke and Kevin Rodriquez of the Virgin Islands.
"Like the primary voters of my congressional district, which Sen. Obama carried, I am inspired by Barack's vision for America, his ability to unify our country and bring much-needed to change to Washington," Mitchell said in a statement Saturday.
Rodriquez had backed Clinton but decided to switch his endorsement, citing Obama's ability to unite the Democratic Party and win the White House, according to Obama's campaign.
Kristi Cumming, named an add-on superdelegate by the Utah Democratic Party late Friday night, also said she will vote for Obama.
U.S. Rep. Ciro Rodriguez of Texas announced his support for the New York senator Saturday, and Arthur Powell was named an add-on superdelegate by the Massachusetts Democratic Party and said he would vote for Clinton.
The Obama campaign had announced the support of seven superdelegates Friday, including one previous Clinton backer. Find out where the superdelegates stand »
A flood of superdelegate endorsements for Obama could effectively end the Democratic race.
Neither candidate has the 2,025 total delegates needed for the nomination. Obama has 1,862 total delegates and Clinton has 1,697, according to a CNN survey.
There are only 217 pledged delegates up for grabs in the remaining contests.
After Clinton's narrow win Tuesday in Indiana and and her double-digit loss in North Carolina, former Sen. George McGovern, the 1972 Democratic presidential nominee, said he had decided to back Obama over the former first lady. McGovern is not a superdelegate.
But Clinton is not going down without a fight, making arguments to superdelegates that she is the best candidate to lead a Democratic ticket in November.
Her campaign tried to appeal to elected Democrats in Republican-leaning districts, arguing that Clinton can win more votes there than Obama and thus help their re-election prospects.
In a PowerPoint presentation e-mailed to the nearly 800 superdelegates, the campaign detailed how she had defeated Obama in GOP-leaning congressional districts and had consistently topped him among key voting blocs such as senior citizens and Hispanics. View the PowerPoint presentation
Despite those efforts, the Clinton camp appears to be planning an exit strategy, according to Lawrence O'Donnell, a Huffington Post contributor who cited Clinton insiders.
"What the senior campaign official has told me is that they will go through the final votes on June 3," O'Donnell said on CNN's "American Morning." "Remember, Hillary is going to win maybe three of the elections, and Obama is going to win maybe three elections coming out of it." Watch what O'Donnell says Clinton insiders are saying behind doors »
O'Donnell said the source told him that the Clinton campaign would make its case to the superdelegates for about a week after the primaries ended.
Meanwhile, former Democratic contender John Edwards said Friday on NBC and MSNBC that Obama is the likely nominee. Edwards is not a superdelegate. Watch as the momentum appears to be in Obama's favor »
Both the Clinton and Obama campaigns have heavily wooed the former senator from North Carolina since he ended his presidential run in January, but he has not publicly endorsed either candidate.
Edwards said Friday that he worried the continuing campaign could take a toll on the Democratic Party's chances in November.
"I think it's fine for Hillary to keep making the case for her," he said on MSNBC's "Morning Joe." "But when that shifts to everything that is wrong with [Obama], then we're doing damage instead of being helpful."
CNN's Steve Brusk, Mark Preston, Robert Yoon, Rebecca Sinderbrand, Richard Allen Greene, Ed Hornick and Alexander Mooney contributed to this report.