The customary tsk-tsks and vapors erupted when President Trump opined on the state of mind of Sen. Elizabeth Warren (D-Mass.) during a New Year’s Eve interview on Fox News. Asked whether Warren thinks she can beat him in 2020, Trump replied, “You’d have to ask her psychiatrist.”

Trump’s critics are so reflexively critical at this point that they can’t recognize a great idea when they hear it. By all means, let’s ask Warren’s psychiatrist — but let’s not stop with Warren. To the couch, Mr. President!

Love or hate him (or anything in between), no reasonable person can deny that Trump is a textbook example of narcissistic personality disorder. Reading the list of symptoms on the Mayo Clinic’s website is like scrolling through the president’s Twitter: “Require constant, excessive admiration,” “exaggerate achievements and talents,” “be preoccupied with . . . brilliance, beauty or the perfect mate,” “monopolize conversations and belittle . . . people,” “expect special favors and unquestioning compliance,” “have an inability or unwillingness to recognize the needs and feelings of others.”

Yet we need not be so clinical to suspect that Trump might fail his inkblot test. Just look back to our opening sentence — specifically the words, “during a New Year’s Eve interview on Fox News.”

Picture this man, this occupant of the highest office in the strongest nation on Earth. In early December, he announced plans to spend the holidays enjoying a restful break from Washington at his palatial Palm Beach retreat. The very picture of sanity, no? If I owned a palatial Palm Beach retreat and didn’t use it to relax in late December, you’d rightly call me crazy.

Yet there sits Trump, far from Mar-a-Lago, holed up inside the White House during a dreary D.C. December, abandoned by his chief of staff, his attorney general, his secretary of defense, etc. He’s fighting a losing battle with Congress over money to build a wall — only it’s not a wall, necessarily. It’s “steel slats,” perhaps. It’s some sort of “barrier,” anyway. Whatever it is, as a candidate, Trump promised nearly every day that it would cost us precisely nada.

Jailed in the White House, hounded by investigations and jabbering himself in circles, he decided to insert himself into the Fox News coverage of New Year’s Eve.

That’s cuckoo for Cocoa Puffs. Holiday cable is to news as cruise-ship theater is to Broadway. Another year at this declining rate, and the president will be calling the sweater-dress ladies on QVC. Two years, and the next occupant might find the White House overrun with cats.

A million erroneous citations notwithstanding, Albert Einstein never said the definition of insanity is doing the same thing over and over and expecting a different result. But wherever it came from, Trump proves the maxim daily. He keeps spouting off, keeps improvising impulsively, keeps spurning those who could help him and antagonizing those who can hurt him, huddles ever closer to the dying embers of his demoralized base — yet seems surprised that things keep going wrong.

In Trump’s defense, I’ve long believed that most presidents could keep a shrink working overtime. Imagine trying to heal Thomas Jefferson’s bifurcated personality: half slavekeeper, half apostle of freedom. Did James Madison’s tiny stature have anything to do with his blustering and blundering into war? Might Franklin Pierce and James Buchanan have avoided the Civil War if the first had been sober and the second free to express his apparent homosexuality?

And the daddy issues. Oh, my. Andrew Jackson never knew his father. Abraham Lincoln disdained his, coolly refusing to attend Thomas Lincoln’s funeral. Franklin D. Roosevelt was a teenager when his invalid father died, and his domineering mother kept him on an allowance even in the White House. John F. Kennedy was, like his brothers, a product of his father’s inexhaustible ambitions. Lyndon B. Johnson was haunted by his father’s failures; Richard M. Nixon by his father’s abusiveness; Ronald Reagan by his father’s alcoholism. Bill Clinton never met his father, and Barack Obama’s was almost entirely absent after the boy’s toddler years.

And would any president other than George W. Bush have been as eager to turn 9/11 into a crusade to oust Saddam Hussein, the Iraqi dictator left in power by Bush’s more cautious father?

By all accounts, Trump was the apple of his father’s eye, and yet the president has spent his career trying to escape his Outer Borough roots and deny his debts to dad.

At this point, I wonder whether anyone who’s not a bit off-kilter has what it takes to win and inhabit the awesome, awful office of the presidency. To offer oneself as decider of the questions too hard for experts to decide. To alter one’s life and the lives of one’s family forever. To live with the nuclear button.

Still, there’s value in knowing. So let’s ask the psychiatrists, Mr. President. And let’s start with yours.

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