Ten months into President Biden’s term, panicky Democrats have already begun to speculate on who might take his place on the ticket in 2024, despite Biden’s assurances that he intends to stand for reelection.

A Post story last weekend contained this remarkable nugget: “One Democrat involved in campaigns said they couldn’t think of a single person they had spoken to in the last month who considers the possibility of Biden running again to be a real one.”

Maybe so. But if there’s one Democrat in Washington who isn’t feeling panicky right now, I’m betting it’s the president himself.

For Biden, being written off as too old and out of his depth isn’t exactly a gut punch. It’s more like another day in the last 30 years.

In 1987, Biden’s first presidential campaign came crashing down in a matter of days amid charges of plagiarism. At that moment, Biden was not quite 45 and had just emerged as one of the brightest hopes of his generation. Almost overnight, he became a casualty of the brand-new character wars, his national ambitions declared dead by the entire media-political class.

If there was any doubt that Biden’s career had been wiped away, the following year he almost literally died from a sudden brain aneurysm. Biden recovered and kept at it.

In 2007, when Biden again decided to seek the presidency, the consensus was that his time had passed — and that Biden must be the only Democrat in Washington who didn’t know it.

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Biden heard the laughter of all the insiders and pundits who said he was over the hill, out of step, comically long-winded. He ended up with the vice presidency.

Eight years later, when Biden — now 73 — considered a third presidential run, the overwhelming sentiment within the party was that Hillary Clinton, and not Biden, was Barack Obama’s best and likeliest successor.

For the third time in his career, all the smart Democrats praised Biden’s service and sent him off into the political sunset. Even most of his closest advisers assumed he was through.

Four years later, he was back, paddling headlong against the ideological current in his party. And again, after he got blasted in Iowa and New Hampshire, everyone who knew anything dismissed Biden as too old and too centrist, not to mention too White and male.

We were wrong. Ploddingly, haltingly, serenely, Biden persevered and won.

So you can imagine how Biden feels now, when he sees these polls that show his approval ratings bobbing around the 40 percent mark and when he hears about all these Democrats — including a few in his own administration — angling to fill the vacuum once he finally realizes he must get out of the way.

You can see him chuckling to himself, the way he sometimes does when a reporter asks some shallow question he’s answered 2,000 times in his life. Keep declaring me finished, Biden must be thinking. Time will decide.

There’s a danger in this, of course. Just because you’ve always defied the groupthink doesn’t mean you’ll do it again — especially if all that perspective fills you with a kind of unexamined confidence.

Whatever his comfort as a No. 2, Biden hasn’t yet adjusted to being the guy who sets the agenda. One hopes that his unsteady performance in trying to pass a social spending bill — adrift and indecisive, too deferential toward the same left flank of his party that he soundly defeated in last year’s primaries — will serve as a turning point rather than a template for the rest of his presidency.

Biden’s age is a legitimate problem, too. He can shrug it off if he wants (and he was lucky to get away with it during a campaign that was largely conducted by Zoom), but running for reelection at 81 would be asking a lot of voters, and his party deserves to see a little more assertiveness in the face of mounting crises.

But what Biden knows, after three-plus decades of being politically left for dead, is that nothing’s over just because a bunch of unnamed staffers who spend too much time reading polls say it’s over. He knows from experience that the more monolithic and reflexive the popular wisdom, the more likely it will be proved wrong.

Does Biden run again? Personally, I’ve always thought he was most likely a one-term, stabilizing president, and I don’t really believe he has made up his mind to seek another term.

But it’s early yet, and I’m pretty sure Biden won’t be spooked into accepting everybody else’s idea of political reality. If there’s any one lesson of his political life, it’s that realities usually change.