Former Vice President Joe Biden made his 2020 candidacy official on Thursday, but even his entry into the crowded Democratic primary field isn’t enough to move former President Barack Obama off the sidelines.

Biden announced his run for president in an online video Thursday, after weeks of speculation and anticipation. After his announcement, Biden was asked why his former boss of eight years isn't publicly backing him.

"I asked President Obama not to endorse,” Biden told Fox News on Thursday outside an Amtrak station in Delaware, adding that “whoever wins this nomination should win it on their own merits.”

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Obama's team released a statement praising Biden on Thursday but didn’t offer an explicit endorsement.

“President Obama has long said that selecting Joe Biden as his running mate in 2008 was one of the best decisions he ever made,” Obama spokeswoman Katie Hill said in a statement Thursday morning. “He relied on the Vice President’s knowledge, insight, and judgment throughout both campaigns and the entire presidency. The two forged a special bond over the last 10 years and remain close today.”

Meanwhile, sources close to the Obamas have told Fox News that the former president has made clear that he doesn’t plan on endorsing early in the primary process—if at all.

“President Obama is excited by the extraordinary and diverse talent exhibited in the growing lineup of Democratic primary candidates,” a source close to Obama told Fox News Thursday. “He believes that a robust primary in 2007 and 2008 not only made him a better general election candidate but a better president, too. And because of that, it’s unlikely that he will throw his support behind a specific candidate this early in the primary process – preferring instead to let the candidates make their cases directly to the voters.”

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Republicans have used the non-endorsement to attack Biden, with RNC chairwoman Ronna McDaniel tweeting that Obama has "chosen *not* to endorse his right-hand man."

But former communications director for the Democratic National Committee and former spokesperson for Hillary Clinton’s 2008 presidential campaign Mo Elleithee said he doesn't view the decision as a snub, saying it is appropriate for Obama to remain on the sidelines.

“I think it’s pretty clear that President Obama wants to play a neutral role in the primary process, and there are a number of candidates in this field that he has a relationship with,” Elleithee, a Fox News contributor and executive director of Georgetown University’s Institute of Politics and Public Service, told Fox News. “I think he wants to focus more on helping set the table for a successful election for the party, rather than necessarily helping to pick the candidate.”

Elleithee said that Obama has praised a number of candidates in the race, but said “he hasn’t put out a statement like he did for Biden today for anyone else.”

“I think Biden holds a special place in Obama’s political heart, and he wanted everyone to know that, without going so far as to put his thumb on the scale one way or the other,” he said.

Democratic strategist and Fox News contributor Jessica Tarlov agreed.

“It’s definitely not a snub at Biden or any reflection of how he feels about his former vice president who he is obviously very close with,” Tarlov told Fox News. “President Obama and Michelle have both made it clear that they want the Democratic process to play out, as it should.”

Despite a lack of an Obama endorsement, Biden was met with support quickly after his official announcement. Sens. Bob Casey, D-Penn. and Chris Coons, D-Del., were among the first to officially get behind his campaign.

Fox News’ Peter Doocy, Kristin Brown and Mike Emanuel contributed to this report.