Suddenly, it’s 2024 all over again.

Once more we’re litigating Joe Biden’s catatonic debate performance, his lumbering gait, his moth-eaten memory and his selfish delusion he deserved a second term in the White House while shuffling through his ninth decade on earth.

Biden’s abrupt announcement he faces an advanced form of prostate cancer has only served to increase speculation over what the president’s inner circle knew, and when they knew it.

“Original Sin,” a book by journalists Jake Tapper and Alex Thompson, published this week, is chock-full of anecdotes illustrating the lengths to which Biden’s family and palace guard worked to shield his mental and physical lapses from voters.

John Robert Greene is not at all surprised.

“It’s old news, hiding presidential illness,” said Greene, who’s written a shelf full of books on presidents and the presidency. “I can’t think of too many … who’ve been the picture of health.”

Before we go further, let’s state for the record this in no way condones the actions of Biden and his political enablers. To be clear, let’s repeat it in capital letters: WHAT BIDEN AND HIS HANDLERS DID WAS WRONG.

But, as Greene states, it was not unprecedented or terribly unusual. History abounds with examples of presidential maladies being minimized, or kept secret.

Grover Cleveland underwent surgery for oral cancer on a yacht in New York Harbor to keep his condition from being widely known. Woodrow Wilson suffered a debilitating stroke, a fact covered up by his wife and confidants, who exercised extraordinary power in his stead.

Franklin D. Roosevelt and John F. Kennedy both suffered serious, chronic ailments that were kept well away from the public eye.

Those surrounding Ronald Reagan downplayed his injuries after a 1981 assassination attempt, and the Trump administration misled the public about the seriousness of the president’s condition after he was diagnosed with COVID-19 a month before the 2020 election.

The capacity to misdirect, in Biden’s case, or mislead, as happened under Trump, illustrates one of the magical features of the White House: the ability of a president to conceal himself in plain sight.

“When you’re in the presidency, there is nothing that you can’t hide for awhile,” Greene, an emeritus history professor at Cazenovia College, said from his home in upstate New York. “You’ve got everything at your disposal to live a completely hidden double life, if you want. Everything from the Secret Service to the bubble of the White House.”

Greene likened the Neoclassical mansion at 1600 Pennsylvania Ave. to a giant fish bowl — one that is painted from the inside. It’s highly visible, but you can’t really see what’s happening in the interior.

That deflates the notion there was some grand media conspiracy to prop Biden up. (Sorry, haters.)

Yes, detractors will say it was plain as the dawning day that Biden was demented, diminished and obviously not up to the job of the presidency. Today, Trump’s critics say the same sort of thing about him; from their armchairs, they even deliver quite specific diagnoses: He suffers dementia, or Alzheimer’s or Parkinson’s disease.

That doesn’t make it so.

“It’s a very politicized process. People see what they want to see,” said Jacob Appel, a professor of psychiatry and medical education at the Icahn School of Medicine in New York City, who’s writing a book on presidential health.

“You can watch videotapes of Ronald Reagan in 1987,” Appel said, “and, depending on your view of him. you can see him as sharp and funny as ever, or being on the cusp of dementia.” (Five years after leaving the White House, Reagan — then 83 — announced he was in the early stages of Alzheimer’s disease.)

To an uncomfortable degree, those covering the White House — and, by extension, the public they serve — are forced to rely on whatever the White House chooses to reveal.

“I don’t have subpoena power,” Tapper told The Times’ Stephen Battaglio, saying he would have eagerly published the details contained in his new book had sources been willing to come forth while Biden was still in power. “We were just lied to over and over again.”

It hasn’t always been that way.

In September 1955, during his first term, President Dwight D. Eisenhower suffered a heart attack while on a golf vacation in Denver. “”It was sudden,” said Jim Newton, an Eisenhower biographer. “One minute he’s fine and the next minute he was flat on his back, quite literally.”

The details surrounding Eisenhower’s immediate treatment remain a mystery, though Newton suggests that may have had more do with protecting his personal physician, who misdiagnosed the heart attack as a bout of indigestion, than a purposeful attempt to mislead the public.

From then on, the White House was forthcoming — offering daily reports on what Eisenhower ate, his blood pressure, the results of various tests — to a point that it embarrassed the president. (Among the information released was an accounting of Ike’s bowel movements.)

“They were self-consciously transparent,” Newton said. “The White House looked to the Wilson example as something not to emulate.”

Less than 14 months later, Eisenhower had sufficiently recovered — and voters had enough faith in his well-being — that he won his second term in a landslide.

But that 70-year-old example is a notable exception.

As long as there are White House staffers, campaign advisers, political strategists and family members, presidents will be surrounded by people with an incentive to downplay, minimize or obfuscate any physical or mental maladies they face while in office.

All we can do is wait — years, decades — for the truth to come out. And, in the meantime, hope for the best.