The highest office in the land has afforded Mr. Trump his most prominent celebrity perch. His account has risen from a few million followers to nearly 20 million in the past year. There was a time when some assumed that Mr. Trump’s public persona would evolve as he rose in the political ranks. But there’s just one Trump, and that’s been key to his success. As Kim Kardashian once said, the secret to social media dominance is authenticity and consistency. Mr. Trump’s projection of realness relies on him being reliably self-aggrandizing and wildly inappropriate. That may seem like a liability for the leader of the free world, but it’s an asset in the low-culture celebrity roles that have led him to this moment: reality TV boss, Howard Stern guest, pro-wrestling heel.

Eight years ago, Barack Obama was the social media wonder headed to the White House, and his tech savvy was heralded as a bright light for democracy. The tweets he posts to @POTUS never seem impulsive; they seem made for posterity. Even his jokes are calculated to be minimally offensive and maximally educational. When the NASA rover Curiosity carried Mr. Obama’s signature to the surface of Mars, Mr. Obama responded in the form of a dad joke: “That is out of this world.”

If Mr. Obama came to power in a time of great optimism for Twitter, Mr. Trump lords over a waning platform. What was once a hopeful place for global connection and resistance has become a site for coordinating harassment campaigns, connecting with white supremacists and accelerating unverified and sometimes dangerous rumors. Its growth has slumped and its stock price has stagnated.

But the place suits Mr. Trump’s purposes fine. For the guy who’s all about appearances, Twitter provides the veneer of populist connection without the hassle of accountability. Sean Spicer, Mr. Trump’s incoming press secretary, has suggested that Twitter town halls and Reddit forums may replace some typical presidential press interactions, where he can easily make himself available to anonymous fans instead of the scrutiny of the press. The social media platforms that were once heralded as democratic tools could also be used to undermine democratic norms.

All of this works because one group is as intoxicated by Twitter as Mr. Trump is: journalists. It’s hard to explain to a normal person — one of the 79 percent of American adults who don’t use Twitter — why the platform mesmerizes the news media. Its all-powerful search function means you can conjure material on any kind of news topic — or just spend your time searching for your own name. Reporters still crave the ego rush of a published byline, but that pales in comparison to the animated feedback loop that Twitter offers. The more time you spend, and the more tweets you send, the bigger your following becomes. But Twitter provides little actual reach — compared with Facebook or Google, it hardly drives any traffic to articles. It’s like a video game for professional validation.

Mr. Trump expertly exploits journalists’ unwavering attention to their Twitter feeds, their competitive spirit and their ingrained journalistic conventions — chiefly, that what the president says is inherently newsworthy. As a developer and reality show star, he lobbied the news media for coverage. Now journalists feel obligated to pay attention to him. Mr. Trump overwhelms the media with boatloads of what was once a rare commodity: access. He creates impressions faster than journalists can check them. By the time they turn up the facts, the news cycle has moved on to his next missive, leaving less time (and reader attention) for the stories Mr. Trump does not highlight on his feed.

Mr. Trump may not follow a deliberate distraction strategy, but he doesn’t need one. He distracts instinctively. All he needs is a phone, the press and whatever thought just entered his mind.