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Former President Barack Obama did something this weekend that he’s been unable to do so far in the Democratic primary race: Call former Vice President Joe Biden and offer his congratulations.

While the two men speak regularly, the call from Obama on Saturday night came after Biden’s victory in South Carolina. But the words of praise for Biden’s commanding finish in the contest did not change the fact that Obama still plans to stay on the sidelines and not insert himself into the primary fight as it intensifies.

A person close to Obama told CNN that the former president’s view has not changed: He has no immediate plans to offer an endorsement of Biden — or anyone — as the nominating contest heads into Super Tuesday.

“We are skeptical that an endorsement coming from us could truly change the political winds right now,” the person close to Obama told CNN. If Obama were to endorse Biden, the person said, there is “a very real chance it backfires.”

But more importantly, Obama still thinks his most valuable role is to try and unify the party.

“He feels that he’s singularly positioned to help unify the party at the end of this,” the Obama confidant said. “And if he were try to put his thumb on the scale now, it would take away his ability to do so when it’s most needed — the general election.”

The person added: “So he’s prepared to play a vigorous role in coalescing the party around the nominee and working to defeat Trump, but weighing in now likely only divides things worse and weakens his standing for when the Party will need it most.”

While Obama may be refraining from weighing in on the race, he has become a central character in the primary fight.

Biden invokes Obama’s name and legacy again and again, vowing to fight to protect Obamacare and other achievements, even as other candidates like Michael Bloomberg also frequently mention his partnership with Obama as the former mayor of New York City.

Obama has implored Democrats to avoid purity tests in their quest to choose the strongest nominee to challenge President Donald Trump. Aides say he intends to avoid injecting himself into the race as long as he can.