Old age is clearly taking hold of President Biden and hobbling his run for the presidency, The Post has learned.

Even serious accommodations that have been made for the 81-year-old — such as note cards at fundraisers, cheat sheets to keep his thoughts straight and crowds from his inner circle who surround him to distract attention from a stiff gait — fail to hide the deterioration that comes with age.

It became all too clear on Thursday night when he referred to Ukrainian President Volodymyr Zelensky as his Russian adversary Vladimir Putin and Vice President Kamala Harris as his own opponent, Donald Trump.

Some of those who observe him and have encountered him, even his supporters, can no longer overlook his gaffes and failures, which have included mis-reads on the teleprompter and one bizarre moment in which he nipped at Jill’s finger during a campaign event.

More than ever before, according to Garrett Ziegler, a self-described researcher with Marco Polo and a former Donald Trump aid: “That empty stare and the open mouth are signs that Joey has lost a step or two or five or six. His synapses have got to be fried.”

As for the finger nipping, Ziegler added, “That was supposed to be funny. But he appears to be in worse shape than he was [at the time of that incident in 2019].”

In terms of recent confusion of facts – like the time when Biden claimed to have been the first black woman to serve with a black president – Bill Stevenson has a theory.

The former husband of Jill Biden, Stevenson – who knew Biden “when he was 29 and running around like a maniac” — claimed to the Daily Mail the union was busted up when Jill had an affair with the future president, a claim Joe and Jill Biden have both denied.

“Maybe the lies and exaggerations caught up with him,” Stevenson alleged to The Post, in reference to Biden’s verbal gaffes.

“Maybe he doesn’t know what’s real and what’s not real. I think the reality has disappeared in many ways. I think it’s catching up. You enhance and lie and let people down and you lose [a sense of] what is real and not real.”

The White House did not respond to The Post’s request for comment.

When he travels on Air Force One, Biden now uses extra short steps in order to minimize the likelihood of stumbling after a number of unpresidential mishaps during his first term.

The effects of aging appeared to be evident during Biden’s recent Hamptons fundraiser in New York. Weeks before George Clooney acknowledged Biden’s mental slippage, high-rolling New Yorkers couldn’t miss it.

“I have a lot of respect for the man, but he should not be running for president,” a one-time supporter, who attended the Hamptons fundraiser and has a history in DC, told The Post.

In full agreement, at around the same time as the Hampton’s shindig where Biden clutched the arm of Jill for support – perhaps a streamline of the ambulating crowd that has been known to surround him as a distraction – Bob Woodward, Washington Post editor and co-author of “All the President’s Men,” described the president’s debate performance as “a hydrogen bomb for him and the democratic party.”

Astonished by recent deterioration, the former DC source added, “He looked so tired and they had him on teleprompter for a [fundraiser] speech. They’re trying to guard him to the best of their capabilities. But it’s just not possible anymore.”

What to know about the calls for President Biden to drop out of the 2024 race:

• President Biden’s poor performance in the first 2024 presidential debate left some Democrats unsure of his fitness for office and future as the party’s candidate.
• More than a dozen congressional Democrats have joined in calling for Biden’s exit from the race. Former Biden supporter George Clooney echoed these calls in an op-ed published in the New York Times just weeks after he helped lead a record-breaking fundraiser for the Democrat.
• Democratic voters have continued to raise concerns about Biden’s nomination since the debate, with speculations and suggestions for replacement nominees running rampant.
• Biden’s former running mate Barack Obama has reportedly been trying to pressure him to drop out, and had prior knowledge of Clooney’s op-ed. Former House Speaker Nancy Pelosi allegedly told Biden he could not beat former President Donald Trump this time around.
• As the Democratic National Convention approaches, California delegates for the Democratic Party are reportedly in disarray as debate over the president’s chances of re-election threatens to tear the party apart.
• However, the Biden campaign has denied any plans for Biden to bow out and for Kamala Harris to step in as the Democratic nominee. Sources close to the president believe he might not be willing to drop out, while other sources claim he is “receptive” to giving up on a second term.

However, that hasn’t stopped members of Biden’s inner circle from making the kinds of adjustments that can keep Biden looking presidential.

There are the aforementioned teleprompters which hand-hold him through many public appearances.

Stabilizing shoes reduce the likelihood of an unsightly spill. First it was Hokas – the Asia-manufactured sneakers that are built for comfort and balance control – and now, according to Ziegler, “he’’s wearing sneakers that look like dress shoes. He should have gone for those from the start and never wore the shoes with the rounded soles.”

Some potential helpers, according to Ziegler are less obvious than others. “His home butts up to Christiana Hospital, one of the best hospitals in Delaware,” said Ziegler of a facility that is actually a few miles away from Biden’s Delaware digs and ranks among the top healthcare facilities in the United States.

“If they want to be discreet, doctors can easily go from the hospital to the house. There are no visitor logs; so nobody knows who goes in and out. And he goes home more often than [Trump] goes to [his Florida home] Mar-a-Lago.”

Speaking of Biden and his need for health-related accommodations, Ziegler pointed out, “This is not just an 81-year-old. He’s an 81-year-old with two aneurysms in his history.”