If President Biden takes the debate stage Thursday night, it will be the most egregious act of political malpractice since Michael Dukakis climbed into that tank.

Only worse. Dukakis had no way of knowing he would look like Alfred E. Neuman doing a cameo in “Stripes” at that military-themed photo op in 1988. However, the potential disaster of Biden’s debate appearance is evident to everyone.

Haven’t these people seen “A Beautiful Mind”?

No, not the “crazy guy whose brain is befuddled by a thousand bizarre conspiracy theories” part. (That’s what Team Trump should watch.)

The “game theory” part.

There are three possible outcomes when Biden steps on that stage to spend 90 minutes sparring with Trump. Two are meaningless, and one could mean the end of Biden’s candidacy.

Outcome number one: Biden wins. Biden’s doctors inject just the right mix of B vitamins and political Viagra, Trump unleashes his inner toddler, and Biden is declared the victor.

So what?

The dirty little not-so-secret about presidential debates is that they rarely matter. Political pundits love to point to Nixon vs. Kennedy and Reagan vs. Carter because they are the exceptions. They had a meaningful effect on the election’s outcome. (And the Nixon vs. Kennedy case is debatable.)

Most debates have the effect of Clinton vs. Dole or Obama vs. McCain. Remember those?

Neither does anyone else.

Biden supporters say that if the 81-year-old can recreate his State of the Union magic with a display of energy and enthusiasm, he’ll put concerns about his age and mental acumen to rest.

Wrong.

Biden could climb out of the pool from the movie “Cocoon” and do a Circe du Soleil ribbon dance Thursday night, but when he bumbles his way through a shoutout to “Egyptian President Sissy El-Spacek” a week later, he’ll be right back at square one.

The debate is a single night. There will be 130 more before Election Day, and everyone will be another test for Joe Biden.

Outcome number two: They both do fine. The usual. Another forgettable presidential debate that allows both candidates to declare victory. How does that help Biden?

Outcome number three: The “McConnell Moment.”

Biden is asked a question, looks into the camera, and freezes like the GOP senator from Kentucky. Nothing. A painful 20 seconds pass, and the Biden candidacy ends, live on national TV in front of 100 million viewers.

OK, that’s not quite right. If Biden does during the debate what he appeared to do at the White House “Juneteenth” celebration or the L.A. fundraiser with Obama last week, his candidacy isn’t over. His entire presidency is.

Whether or not the Cabinet invokes the 25th Amendment, Biden will no longer be a player in American politics.

And it doesn’t have to be a frozen moment. It could just be a rambling, incoherent answer that convinces voters Biden is no longer viable as a president.

Ask Republicans about the debate, and some are absolutely certain that will be Biden’s fate. They’re wrong. It’s more likely Biden gets through just fine.

But does any Democrat doubt that a campaign-ending moment is possible? And not “win the lottery” possible, but say, a one in 10 chance?

Why would Biden take that risk? Who would get on a train that had a one-in-10 chance of crashing? Why do that with your political career?

Some pundits argue that, due to concerns about Biden’s age and impairment, he has no choice. Nonsense. “As president, I cannot demean the office by debating a convicted felon.” Done.

Would Biden take a hit for refusing to debate? Sure. But “Take a Hit” is a hell of a lot better than “Back to Delaware!”

The math is simple: For Trump, this debate risks nothing. The only way Trump could surprise anyone Thursday night would be to show up and act like a gentleman.

But for Biden, this debate risks everything. Thirty seconds of excruciating video and, no matter how many times Karine Jean Pierre chirps “Cheap Fake” from the White House press room, his presidency is over.

How does this make sense?

The chances are Biden will be OK, and the race will return to the swing-state slog that’s been underway for months.

But if he does have a campaign-ending moment at this entirely optional event, Biden will have committed the most significant political blunder in presidential history.