When he was running against Mr. Cruz, no one cared — at least no Democrats — that he was a three-term congressman from El Paso who didn’t have much to show for his time in Washington. Running as an outsider was a good thing, especially when the insider he was running against was one of the most unpopular senators in the history of, well, the world.

But in the crowded field that is the 2020 Democratic slate, Mr. O’Rourke has looked like what he is: a novice. Candidates to the left and the right of him have more experience, more knowledge and more ideas, which was painfully obvious during the first debate, when his fellow Texan Julián Castro seized the opportunity to school Mr. O’Rourke on immigration reform. Anyone who conjured the specter of a Trump-O’Rourke race around that time would picture Freddy Krueger moving in on Winnie the Pooh.

Then, too, the flip side of charisma is narcissism. That long bipartisan, cross-country ride with Will Hurd, a Republican Texas congressman, was a great intro back in the day, as was much of the up-close-and-personal social media employed in Mr. O’Rourke’s Senate campaign. But nationally — when “Beto” was already a household name in many states — the same technique made him look just silly, or worse. Live streaming his dental visit during the crisis on the Texas-Mexico border? “I want to be in it. Man, I’m just born to be in it,” Mr. O’Rourke told Vanity Fair, which wasn’t the best explanation for competing to be the leader of the free world.