The office of the president of the United States is known for wearing down the mere mortals who hold it. At the very least, it prematurely ages its occupants.

Often, it humiliates them, forcing them to rehabilitate their reputations later (Jimmy Carter and the late George H.W. Bush). In the worst cases, it chews them up and spits them out (Lyndon Johnson and Richard Nixon).

It is a journalistic trope that this is happening to President Trump before our eyes. The media constantly write stories about how the president is panicked and cornered, barely able to handle his duties, as the walls perpetually “close in.”

But as far as any outside observer can tell, he’s as ebullient and combative as ever, and has never blinked, no matter how intense the pressure of any given controversy.

Far from getting crushed by the weight of the office, Trump doesn’t seem to feel it at all. Never has any president been as outwardly unfazed by the majesty of the presidency and the White House, or made fewer accommodations to their trappings and norms.

President Trump still acts like he’s Celebrity Trump fighting a vicious flame war with Rosie O’Donnell, except his targets now might be other heads of state, or his own attorney general, or losing members of his own party.

The idea that he is a representative of the nation apparently makes very little impression on him. He never stops to think that any given jibe might be unworthy of the highest office in the land, or maybe that he, blessed with more power and showered with more attention than anyone on the planet, has an obligation to be elevating and restrained, even if no one else is.

One of the attractions of the presidency to him appears to be that he can continue to punch down — but do it from a higher altitude than ever before.

To draw on examples from just this past weekend, he inveighed against stupid skits mocking him on “Saturday Night Live,” going so far as to question their legality. He called his former lawyer and fixer Michael Cohen “a rat,” using terminology favored by the mob (although usually in private).

And he commented on the pending prosecution of Maj. Matthew Golsteyn, a US Army officer who is facing murder charges for allegedly killing a Taliban bomb-maker in 2010 while Golsteyn was deployed in Afghanistan.

Even after two years, Trump hasn’t lost his capacity to surprise. Did the president of the United States really render the last name of the incoming chairman of the House Intelligence Committee, Adam Schiff, as an expletive?

Did he call that TV anchor “low IQ”? Did he insult the looks of Stormy Daniels, the porn star with whom he allegedly had an affair? Did he call his former secretary of state dumb?

Of course he did.

In the competition between blurting out whatever happens to be bothering him and paying a little heed to acting presidential, it’s never a contest.

This doesn’t mean that Trump should give up his enormously powerful megaphone on Twitter, or pretend to be something he’s not (even if he could). He just shouldn’t go out of his way to affirmatively advertise his animosities and half-baked opinions.

Much of this is ephemera, but collectively and over time, it creates a lasting impression. A major factor in the drubbing that Republicans suffered in the suburbs in the November midterms was a reaction against Trump’s persona, as underlined by his own conduct and tweets.

If he cares about keeping the presidency — and he surely does — he should care a little more about respecting the dignity of the office.

The great advantage of the presidency is that it is naturally set up to invest people elected to it with a certain grandeur, via the White House, saluting Marines, Air Force One, “Hail to the Chief,” and ceremonial events large and small.

All it requires is showing up and, very often, reading from a script. Rather than simply pocketing this benefit, Trump tends to undercut it 280 characters at a time.

If he’s ever brought low, it’s less likely to be from the pressures of his responsibilities than his cussed inability or unwillingness to make a minimal effort to conform to his role.