McCLELLANVILLE, S.C. – As the race for the Democratic presidential nomination cruises toward a potentially decisive Super Tuesday, one Democratic superstar with the power to alter the course of the contest is clinging steadfastly to the sidelines: Barack Obama.

Those close to the former president expect him to stay there.

Wildly popular within the party, Obama has mostly avoided a contest that features his former vice president, Joe Biden, even as his legacy on health care, immigration and other issues has played a central role in debates and advertising by the candidates so far.

As they crisscross South Carolina ahead of the state's primary on Saturday and the 14 states that make up Super Tuesday on March 3, several candidates – including Biden and former New York Mayor Michael Bloomberg – are touting their ties to Obama.

JoAnn Thompson, 64, a retired teacher from Pawleys Island, S.C., said Obama "just might" endorse but said that neither Biden nor anyone else should count on it.

"It would be great if he does,” said Thompson, who is undecided.

But, she added, Biden "can do it on his own. He’s going to be president, not Obama."

Obama is aware of the "agita" among some centrist and establishment Democrats about Sen. Bernie Sanders' surge after strong finishes in Iowa and New Hampshire, but has "always been a believer in the nomination process" and feels "voters themselves must pick our nominee," according to a source familiar with the former president's thinking who spoke on the condition of anonymity to discuss internal strategy.

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"President Obama is uniquely positioned to help unify the party once we have a candidate," the source said. "If he were to try to put his thumb on the scale now, it would limit his capacity to do so when his voice is most needed: The general election."

Obama, who tied with President Donald Trump for the most admired man in America in a Gallup poll this year, hasn't remained completely silent. He made an appearance in the race Wednesday by demanding that South Carolina television stations and a pro-Trump group stop airing an advertisement that used his voice to attack Biden.

The ad, aired by the Committee to Defend the President super PAC, recycles an attack used in a Georgia congressional race in 2017. It includes audio of Obama reading from his memoir, "Dreams From My Father," about Democrats who only court black voters at election time. But in the book, Obama is paraphrasing the words of someone else.

More:Obama demands TV stations stop airing 'despicable' anti-Biden ad

Obama spokeswoman Katie Hill described the ad as "despicable" in a statement.

"President Obama has several friends in this race, including, of course, his own esteemed Vice President," Hill said in the statement.

Still, Hill said, Obama "has said he has no plans to endorse in the primary."

Biden is leading in polls in South Carolina, but his position is shakier in some of the biggest Super Tuesday prizes, including California, Texas and North Carolina. Though Biden built his campaign around a theme of electability, it is Sanders who has emerged as the party's frontrunner.

Obama's legacy has never been far from center stage as the candidates have debated what kind of party will emerge in response to Trump's presidency, and what kind of candidate is best positioned to beat him. Sanders has sought to steer the party left, such as by upending Obama's signature health care law and replacing it with a Medicare-for-All, government-run insurance system.

Without saying a word, Obama became an even bigger factor in the race recently when Biden began accusing Sanders of contemplating a primary challenge to the incumbent president in 2012. Sanders has denied the claim, but Biden has doubled down with an advertisement making the same allegation.

Biden, sporting his trademark aviator sunglasses at a rural South Carolina health center Thursday, repeatedly named Obama in his remarks. He said he worked with Obama on health care policy, including to secure money for clinics in underserved areas.

"I was proud to work with President Obama to get that done," he said.

All of the focus on Trump's predecessor has raised speculation in some quarters of the party about his role in the race, particularly after a report in Politico last year indicated Obama had relayed privately he might intervene if Sanders was running away with the nomination. Allies have denied that Obama ever made such an assertion.

By jumping into the race now, Obama would risk souring his popularity with a large segment of the Democratic Party – even though it's not clear his endorsement would fundamentally change the shape of the contest. And it would make it far harder for him to play the role of peacemaker after the contentious fight for the nomination is settled.

"I think there are only a handful of people whose voices really make a difference. Certainly President Obama's would," said Rep. Dan Kildee, D-Mich., who added House Speaker Nancy Pelosi's name to that list, along with Rep. John Lewis, D-Ga., and Rep. Jim Clyburn, D-S.C., who did endorse Biden earlier this week.

More:South Carolina kingmaker Rep. James Clyburn endorses Joe Biden

"They could be justified in weighing in," Kildee said, "but they could be equally justified in trying to be that source of unity after we have a nominee. I think right now, if they were to ask my advice, I would say that's going to be a more important role that they could play then trying to shape the race."

Those close to Obama appeared to agree with that assessment. Dan Pfeiffer, who served as a top aide to Obama, described him as "the person with the best ability to unify the party at the end of the process." Pfeiffer disagreed with the notion that Obama would have a harder time as peacemaker if the nominee is Sanders, who represents a significant break with many of Obama's policies.

"I think the opposite is true," he said.

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For Democratic voters attending the Biden health care event in this small fishing town on the Atlantic Coast, Obama remains a revered figure. Few seemed concerned about the former president's moves in a contest that will have major implications for the party.

Voters said it would be fine if Obama endorsed, but they don’t think it is necessary.

Linda Lynah, 66, said that some candidates may be "on edge" about Obama’s endorsement, but said the president is under no obligation. She said she was confident that Obama would at some point endorse Biden, but did not know when.

“It’s really hard to say when it will happen,” said Lynah, who lives near North Charleston, S.C. “The two of them really worked well together."

Charles Johnson, 79, from McClellanville, speculated that Obama didn't want to give any candidate "an unfair advantage" this early.

Obama’s silence, he said, carried an implicit message: “All of them are qualified.”

“So he’s going to wait and see.”

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Contributing: Christal Hayes, Savannah Behrmann