There’s a germ of a good question there, one whose answer we’ll probably never know. The obvious reason that Obama didn’t back Biden sooner is because he didn’t want to be seen as putting a thumb on the scale in the primary, especially on behalf of a candidate who’d fared dismally during two previous runs for president. In a way it was a no-win situation for O. If he backed Biden early and Biden won, the left would resent him bitterly. (They already resent him for not ushering in a socialist revolution.) It’d be another establishment intrusion aimed at thwarting Bernie Sanders’s far-left populism a la the DNC tilting the playing field towards Hillary Clinton in 2016. Even if the left ended up forgiving Obama, Trump would taunt Biden ruthlessly over it. “Sleepy Joe had to be carried over the finish line by Barack!”

Whereas if Obama backed Biden early and Biden lost — a perfectly plausible outcome given his track record — then O would look like a chump. The most popular man in the party would have had his favored candidate rebuked on a national stage, in the brightest spotlight. It would have been humiliating.

The good question lurking in Trump’s question, though, is who did Obama really want to win? Yeah, Joe’s his friend and former VP, but you have to believe O would naturally be inclined towards younger, more charismatic candidates in the Obama 2008 mold. Julian Castro? Cory Booker? Pete Buttigieg? Or did he favor a more pragmatic choice like Amy Klobuchar, someone who could occupy Biden’s centrist niche without any of Joe’s appearance of senescence?

Maybe he really did favor Biden. Joe was the overwhelming choice of black Democrats, the same base that propelled Obama to the presidency. If it’s true that a Democratic nominee can’t win the White House without strong enthusiasm among black voters, and it very well may be, then O might have deemed Biden the pragmatic choice after all. He was the only candidate capable of building a winning coalition, it seems.

Anyway. The Obama endorsement is finally coming now that Bernie’s vacated the field. Democrats — and maybe Obama himself — can’t farking wait:

The former president has stayed out of the Democratic primary, but sources say he is anxious to endorse his former vice president, Joe Biden, and become an active player in the general election campaign against President Trump…

“IT IS TIME,” Doug Landry, a former Hillary Clinton aide, wrote Wednesday, tweeting a cartoon image of Obama as superman. “RELEASE THE SUPER SURROGATE.”…

“He’s eager to go,” said one source close to Obama. “He’s been waiting for this election for almost four years.”…

“No one has heard from him in a long time, and people will pay a lot of money to hear from him, even on a computer,” one longtime Obama ally said…

“Seeing Obama on the campaign trail should excite voters who’ve longed to see him weigh in on current issues and give Biden the needed push,” said Basil Smikle, who served as the executive director of the New York State Democratic Party and a former aide to Clinton. “Obama would also remind voters of his competence while in office, creating a strong contrast between Trump and the Democratic alternative.”

He’ll help Biden a lot with fundraising, no doubt. Not just because of his much greater star power but because, as noted in the excerpt, there’s a degree of mystery about how eager Obama might be to mix it up with Trump. Presidential etiquette suggests that a predecessor shouldn’t charge hard at his successor, but presidential etiquette also suggests that the successor shouldn’t routinely attack the predecessor’s administration and Trump threw out that rule long ago. Democrats will be spoiling to see Obama hit back at Trump on matters like Russiagate, the Ukraine matter, and the coronavirus response.

But I don’t know if O’s going to give them that. The more he hits Trump, the greater the risk that this becomes an “Obama vs. Trump” narrative, which will overshadow Biden. And Obama understands keenly after his party was brutalized in two midterm elections during his presidency that he’s a powerful foil for Republican politicians. If you want to get righties mad and spike their enthusiasm to turn out, show them a clip of Obama yelling at them. Trump understands that too and will seize any opportunity to make this a “Trump vs. Obama” race.

Which is why I suspect O will choose a different tactic. Instead of mixing it up, he might take the high road and conspire with Biden to present an “adults in the room” image to the public. That’s not always easy for a 77-year-old who sometimes loses his train of thought in interviews but it’s easy enough for Obama. Democrats are going to run this fall on a message of “Haven’t you had enough of this incompetent circus?” The strategy, then, should be to present themselves as competent and not a circus. Neither party’s nominee seems fully coherent at times, but Obama can manage it. He’ll try to draw more of an implicit contrast with Trump via a “presidential demeanor” or whatever, I’m guessing, then go after him directly.

Speaking of incompetent circuses, BuzzFeed reports that former Hillary staffers organized a Zoom conference call this afternoon to toast to the demise of Bernie Sanders’s campaign. Word got out, of course, irritating Bernie fans at a moment when Biden is eager to reconcile with them. The call has now been canceled. Hoo boy.