Many are billionaires or bigmouths whose outsize vanity mirrors Trump’s. Rick Perry came to his assignment as energy secretary from a stint on “Dancing With the Stars.” Carson’s palatial Maryland home has been described as a gaudy shrine to … Ben Carson, with plaques that honor him and photographs that glamorize him on prominent display.

Every president in my lifetime has been conceited. It’s more or less a job requirement. Bush had a bloated faith in his gut and his charm, while Obama fancied himself the smartest, most soulful person in almost any room.

But they were nothing like Trump, who’s a preening cartoon. He brags like he breathes. It’s autonomic. And he gloats the way our parents and teachers always told us not to.

But that admonition predated Twitter, Facebook, Instagram. Social media have blurred the line between sharing and showing off, and they’ve turned self-promotion into a tic. In our private and our professional lives, we’re prodded to burnish our images, to advertise our assets, to sell, sell, sell. Is it any wonder, then, that we looked up on Friday to see, in front of the Capitol, taking the oath of office, a gaudy confidence man who’s all about the sale? Is it any accident?

His campaign was an unprecedented orgy of self-congratulation. At the start of almost every rally, he trumpeted his poll numbers, and I don’t mean a few quick bleats — I mean a vulgar music that could go on for minutes. At the conclusion of almost every debate, he announced how brilliantly he’d done.

When he stepped up to a microphone to introduce Mike Pence as his running mate, he seemed to forget all about him, and instead paid tribute to himself in a rambling soliloquy more than 20 minutes long. He didn’t stick around onstage for Pence’s remarks.

At the Republican National Convention, warning of national decline, he thundered, “I alone can fix it.” And in the months before and after, he complimented himself out loud and lavishly on everything from the magnitude of his wealth to the majesty of his phallus. That might have disqualified him in another era, but Americans stomached it. More than that, they rewarded it, proving that ours is a different moment, with different mores.