Maybe he suspected people were looking down on him; he strikes me as a man with a chip on his shoulder about … something. Or maybe he was looking down on them. Those who have worked with Mr. DeSantis have said he considers himself the smartest guy in any given room. This is not uncommon among politicians — especially the men. But he had the added problem of being unable to hide his arrogance and discomfort. Superciliousness is not a great way to win support, especially in a political party defined by its hostility toward pointy-headed know-it-alls.

Mr. DeSantis might have been wise to work on his media skills. It’s not that he was a hopeless interview. He is articulate and, as previously mentioned, has perfect hair. But he also frequently sounded canned, overamped and just plain awkward. His voice is kind of high and nasal, making him sound perpetually whiny. (Is that his fault? Nope. Does that make it less grating? Nope.) He bobs his head enough to cause motion sickness in viewers. And he just isn’t much fun — even when interviewers try to help him out, as when Laura Ingraham of Fox News tried to mix it up over college football. Florida State was denied a playoff spot in favor of Alabama, Ms. Ingraham’s pet team, and she was looking to stir up some sparks. But Mr. DeSantis just … dropped the ball.

This is about more than Mr. DeSantis being a smarty pants, rude or snappish. I mean, Mr. Trump has never paid much of a price for trash-talking his critics. Reaching back, Barack Obama was, quite fairly, accused of seeming aloof, condescending and professorial. But both Mr. Obama and Mr. Trump are clearly comfortable in their own skin, and nothing may be more appealing, and reassuring, in a leader than this kind of loose-limbed self-assurance.

But DeSantis? Oy. Everything about his body language screamed, “I am uncomfortable!” Whether he was sipping a beer, one hand awkwardly perched on his hip, or standing stiffly on stage at a CNN town hall, his fingers nervously skittering across his thumb, over and over again.

Once a candidate gets stuck with the “stiff and awkward” label, it is nearly impossible to shake. Occasionally, someone finds a way to turn it into an asset, at least in the primaries. In his second run for president, the stodgy, patrician Mitt Romney wound up looking like the serious, thoughtful grown-up of the pack, and plenty of people in the old G.O.P. liked that. Who knows? Maybe Mr. DeSantis will find his way forward in a future campaign. But this time, he just never made the gut-level connection with voters needed to let his candidacy catch fire. Instead, he found himself the target of a million memes, not to mention a satirical “Daily Show” video of him standing on a debate stage, giving himself a pep talk on how to look normal.