Why isn’t Obama just endorsing Hillary Clinton?

President Obama has met one-on-one with Hillary Clinton in private several times over the past few months. His staff and her campaign staff communicate often. He has seen many of his top aides go to work for her. And now, in a podcast released Monday morning, he came very close to endorsing her as his successor in the White House. Close — but then he didn’t actually explicitly do it.

Vice President Biden’s October announcement that he would not run in 2016 removed an obvious conflict for Obama — an impossible choice between two people he calls friends. But in the ensuing months, the president has not offered an endorsement.

“To be clear, we have never ruled out an endorsement in the primaries,” White House spokesman Eric Schultz told Yahoo News on Monday. “We’ve just said that [the president] will have the opportunity to vote in the Illinois Democratic primary, and it’ll be up to him if he wants to make that public.”

The president, refusing to side with his former secretary of state, a former senator and first lady, over self-proclaimed socialist Bernie Sanders? What does that say about their relationship — or his confidence in her as commander in chief?

Very little, as it turns out. With one interesting exception (Bill Clinton), recent presidential history shows that sitting presidents tend to make their presidential endorsements late in the primary game. Very late.

In fact, Obama wouldn’t be out of step if he waited until after the Democratic nomination was no longer in doubt. George W. Bush endorsed Sen. John McCain in March 2008, only after it became clear he would be the Republican nominee. Ronald Reagan waited until May 1988 to endorse his vice president, George H.W. Bush, only doing so after his lone rival dropped out. Lyndon Johnson waited until weeks before the 1968 election to endorse Hubert Humphrey. Only Bill Clinton endorsed his vice president, Al Gore, before a single primary ballot had been cast, in December 1999 — at a time when former New Jersey Sen. Bill Bradley looked like a strong challenger.

“As president and symbolic head of the Democratic Party, he doesn’t want to officially take sides in an intraparty fight. This isn’t unusual for a sitting president,” Matt Dickinson, a political science professor at Middlebury College, told Yahoo News.

“This doesn’t mean Obama can’t indirectly signal his preference. In fact, I think Obama made it clear in the [Politico] interview that he prefers Clinton,” Dickinson said.

In that back-and-forth, Obama denied that Sanders reminded him of his 2008 self — a passionate outsider candidate taking on Clinton. He also suggested that Clinton, while “really idealistic and progressive,” is perhaps more ready to govern and has suffered from the perception of her as the establishment candidate.

“Bernie came in with the luxury of being a complete long shot and just letting loose,” Obama told Politico. “I think Hillary came in with the both privilege — and burden — of being perceived as the frontrunner … You’re always looking at the bright, shiny object that people haven’t seen before — that’s a disadvantage to her.”

And then Obama gave perhaps the biggest clue to why he has stayed out of the Democratic fray, saying: “Here’s my view: That whoever the nominee is, is going to need the other person’s supporters.”

Several former aides to Obama’s campaigns and the White House told Yahoo News that the president sees his most important task in 2016 as uniting Democrats in the general election against the Republican candidate.

“The most important political goal he has left is to make sure one of these Republican candidates doesn’t win,” his former chief speechwriter, Jon Favreau, told Yahoo News. “If he endorses Hillary now, and then Bernie wins in some crazy — and in my view — highly unlikely turn of events, it hurts [Sanders] as the nominee.

“So why risk that when it seems like Hillary will be able to pull this out on her own?” Favreau said.

The coyness comes from the top. Roughly a year ago, Obama declined to say whether he preferred to see Clinton or Biden succeed him.

“I love ’em both,” he said. “Good try.”

The White House has also played down concerns that a bruising primary fight could damage the eventual nominee.

“Nobody in the White House is losing any sleep over the prospect of a vigorous Democratic primary campaign,” White House press secretary Josh Earnest said at his Oct. 26 briefing.

“I’m confident that whoever the Democratic nominee is, they’re going to be pretty eager to have President Obama’s support,” Earnest predicted at his Jan. 11 briefing.

In a Jan. 10 appearance on “Meet the Press,” White House chief of staff Denis McDonough promised that “we’ll do exactly what has been done in the past, which is when the nominee will be set, then the president will be out there” campaigning for his party’s next would-be leader.

That could take some time if the Clinton-Sanders duel turns into months-long political trench warfare — something like the Clinton-Obama battle eight years ago, which only ended in June.

Still, those hoping that Obama will endorse during the Democratic nomination fight may yet get their wish in just over a month: The Illinois primary is March 15.