It wasn’t the tone or content of Trump’s 37,300 tweets. Instead, it was the possible unconstitutionality of how he uses the social media platform’s block button.

The plaintiffs, represented by Columbia University’s Knight First Amendment Institute, were seven individuals — ranging from a freelance journalist to a New York comedian to a Texas police officer — who had sent negative replies to an @realDonaldTrump tweet and were subsequently blocked by the president.

Though Trump’s Twitter account purports to be personal, the plaintiffs argued, his writings invariably involved US government business and executive opinions — making his posts a public forum to which all American citizens should be guaranteed access.

Though @realDonaldTrump reads like the unabridged representation of a singular man’s impulses, three other defendants were named in the suit, which is expected to be ruled upon in the southern district of New York in the coming months.

pic.twitter.com/abH0KoErIA

— Dan Scavino Jr. Archived (@Scavino45) May 2, 2018

One of them was Hope Hicks, the 29-year-old former model who had spent three years as Trump’s media liaison, before leaving the White House in late March.

A second was Trump’s press secretary, Sarah Huckabee Sanders, the president’s designated mouthpiece. But the third, unlike Hicks and Sanders, was someone most of us have never heard of: a man named Dan Scavino Jr.

Scavino was another of the ‘originals’ on Trump’s 2016 campaign, and I saw him numerous times on the trail, but I could never quite ascertain what he was doing to further his boss’s presidential ambitions.

Aggressively nondescript, Scavino, in a suit, would stand at the side of the stage, taking photos of the immense rally crowds with his iPhone and, later, while scowling at his laptop aboard Trump’s 757, post the images to Facebook.

The other fixtures on Trump’s plane — Hicks, the campaign manager, Corey Lewandowski, the policy adviser, Stephen Miller, and the security director, Keith Schiller — had roles that, in a famously unorthodox campaign, at least seemed familiar. But Scavino’s sole task, from what I could tell, was to document Trump’s popularity.

My perplexity over Scavino deepened after Trump’s inauguration, even as Scavino got an official title: assistant to the president and director of social media, a position that had never existed before and one that paid him the maximum White House staff salary of $179,700.

The Trump White House continued to employ an official photographer (Shealah Craighead), as well as a chief digital officer (Ory Rinat). This small digital team shared a suite across the street, in the Executive Office Building.

But Scavino got an office on the ground floor of the West Wing, just down the hall from the leader of the free world.

The only official function Scavino filled that might justify his salary and his prime White House real estate was detailed in the lawsuit’s stipulation of facts.

“Scavino,” both parties to the lawsuit agreed, “assists President Trump in operating the @realDonaldTrump account, including by drafting and posting tweets to the account.”

No-one else, besides Trump, had access to the most consequential and controversial social media account in the world.

A couple of months after the lawsuit was filed, I visited the White House to inform Hope Hicks that I wanted to write about Scavino and his value to the president.

Hicks was not enthusiastic. The story had been done, she said vaguely, before adding that Scavino was himself unlikely to pull back the curtain any further about his life — and besides, she hastened to assure me, there wasn’t much of a curtain to pull back. (Scavino declined to be interviewed for this article.)

Dan, she said, was a selfless public servant who worked tirelessly for the president of the United States. As to his actual value, Hicks offered a curious descriptor I would also hear from several others: Scavino was “the conductor of the Trump train.”

The highly anticipated meeting between Kim Jong Un and myself will take place in Singapore on June 12th. We will both try to make it a very special moment for World Peace!

— Donald J. Trump (@realDonaldTrump) May 10, 2018

For those who have forgotten the history of that phrase, the ‘Trump Train’ began early in the campaign as a quixotic rallying cry. At the time, Trump’s presidential ambitions seemed like a populist burlesque, rather than anything that could seriously be called a political movement.

But the reality-TV star’s fan base continued to grow, in defiance of polling and Beltway groupthink and in direct proportion (or so it seemed) to his mounting pile of scandals and outré policy proposals.

The Trump Train, it soon became clear, was a juggernaut, and before long the phrase became second only to “Make America Great Again” as Trump fans’ most cherished meme.In hindsight, the phrase’s rise is also a good illustration of why Scavino, as the behind-the-scenes cheerleader and relentless documentarian of the Trump movement, deserves significant credit for its success.

Perhaps the most profound effect of Scavino’s countless iPhone videos and photos is that they served as proof to so-called ‘shy Trump supporters’ that they were not alone — that they were (regardless of what the mainstream media reported) poised to make history.

As Jason Miller, the campaign’s senior communications adviser, puts it: “You could make the case that without Dan fulfilling his core mission of conveying the excitement, people wouldn’t have realised that they were part of a movement. It was absolutely critical in encouraging people to turn out.”

But now that they had turned out for Trump and he was America’s 45th president, what did he still need Scavino for? I spent the next six months trying to find out, even as the ranks of ‘originals’ dwindled.

I am pleased to inform you that Secretary of State Mike Pompeo is in the air and on his way back from North Korea with the 3 wonderful gentlemen that everyone is looking so forward to meeting. They seem to be in good health. Also, good meeting with Kim Jong Un. Date & Place set.

— Donald J. Trump (@realDonaldTrump) May 9, 2018

Keith Schiller left in September. Soon after Hope Hicks exited the building, on March 29, Scavino — now the longest-tenured Trump employee in the White House — took over her office, just outside the Oval. By these measures, he was one of the most powerful people in Washington, despite the fact that no-one could explain what Scavino did for a living.

Back in November, 2013, before Twitter had fully transformed into the cesspool of outrage and vitriol it is today, a 37-year-old man named Dan Scavino posted his own contribution to a trending hashtag, #MentionSomeoneYoureThankfulFor.

“Simple!” he wrote. “I would not be where I am today w/o him. Thank you @realDonaldTrump!!”

Scavino was then leading the placid life of a suburban striver. Together with his wife of 13 years, their two sons and two Portuguese water dogs, he lived in a four-bedroom house in Dutchess County, N.Y., looking out onto the sixth hole of the neighbourhood golf course.

An English schoolteacher’s son, he had played tight end and defensive end on his high school football team the year they won state and had kissed the ring of Pope John Paul II.

He had twice finagled front-row seats to see the pope, just as he had talked his way into a sales job at Coca-Cola, while polishing the company president’s golf clubs during his summer employment as a caddy.

.@realDonaldTrump, taking part in "take your child to work day", invited children of White House Staff and White House press corps into the Oval Office for a group photo. #TakeOurChildToWorkDay #TakeOurChildrenToWorkDay pic.twitter.com/77gJJpmWcU

— Doug Mills (@dougmillsnyt) April 26, 2018

His genial hustling had earned him minor celebrity upstate: Scavino frequently dropped in on the studio of the K104.7 ‘Woodman in the Morning’ radio show, and, as a philanthropically minded Catholic, he could be counted on to judge a charity cupcake contest and to walk the runway in a ‘Best Legs in the Hudson Valley’ competition.

But what propelled Scavino’s ascent was his relationship with Donald Trump. The two first met in 1990, when Scavino was a teenage caddy at a Westchester County course that Trump would eventually purchase and rename the Trump National Golf Club.

Scavino carried Trump’s clubs, earning a $200 tip from the developer — who, later, in the club’s Grille Room, told the caddy: “You are going to work for me one day.”

Scavino majored in communications at the State University of New York, in Plattsburgh; he did a six-month internship at Walt Disney World, then later got a job with the Texas-based Galderma Laboratories, as a pharmaceutical rep; he married and settled down.

But throughout it all, he held onto the two hundred-dollar bills that Trump had given him.

When that same Westchester golf club, which now bore the billionaire’s name, offered Scavino a job as an assistant manager, in 2004, he accepted. Four years later, he was the club’s general manager, whizzing around America in the big man’s private plane.

After a brief and not altogether successful stint running his own consulting firm, Scavino reached out to Trump’s son, Eric, in November, 2014, to see if he could come back into the fold.

On November 8, having heard the rumours of a possible presidential bid, Scavino buttonholed his old boss at Eric’s wedding and said: “When you run, I’m in.”

What Scavino was offering were the services of a registered independent, who had no experience in politics. He had only one qualification: He was a Trump die-hard.

Lewandowski hired him on the spot. In June, 2015, the two men, along with Hicks and the political adviser, Sam Nunberg, moved into a cramped office on the 24th floor of Trump Tower.

Scavino’s first assignment was to try to find big-ticket contributors to Trump’s campaign, an effort that proved fruitless, as the Republican donor class did not take his candidacy seriously.

Scavino would later be enjoined to cultivate relationships within the Republican National Committee, which, at that time, viewed the bombastic New York businessman and reality-TV star with eye-rolling scepticism. He had no luck with that effort, either.

A more suitable job for Scavino materialised shortly after Trump’s formal announcement of his candidacy on June 16, 2015.

The campaign had been trying to curry favour with the powerful publisher Joe McQuaid, whose endorsement in The New Hampshire Union Leader was among the most highly coveted in the early primary states.

But this charm offensive threatened to come undone when, during Ivanka Trump’s visit on June 24 to announce the opening of a campaign office in Manchester, McQuaid’s daughter was unable to get her photo taken with the socialite. Trump was infuriated when he learned of this.

To prevent similar dust-ups in the future, Scavino had another duty added to his portfolio: going to the early primary states to tend to the needs of the local kingmaker.

In this new role of going to the early primary states to tend to the needs of the local kingmakers, as with so many of his roles for Trump over the years, Scavino continued to serve as a kind of caddy.

Our two great republics are linked together by the timeless bonds of history, culture, and destiny. We are people who cherish our values, protect our civilization, and recognize the image of God in every human soul. pic.twitter.com/01c8iSGDB3

— Donald J. Trump (@realDonaldTrump) April 24, 2018

He went to McDonald’s and KFC on food runs for Trump. He faithfully typed out tweets as Trump dictated them.

He also wandered the events, climbed the rafters, and snapped smartphone pictures, which he then posted on both his and the campaign’s various social-media accounts.

It happened that the campaign already had a professional photographer on the payroll. But this was becoming a liability, in that she tended to take hundreds of images at each event, and the candidate would insist on spending hours of valuable time poring over every last one of them.

The campaign did nominally have a social media specialist — Justin McConney, son of the Trump Organization’s controller — but he lacked Scavino’s instinct for the base, and in any event, McConney was stationed back at Trump Tower, away from the real action on the campaign trail.

By early 2016, Scavino had become both the Trump campaign’s travelling photographer and its social media chieftain. And because the self-funding candidate had no intention of spending a dime on media coverage, Scavino, with his Facebook videography, also became the closest thing the Trump campaign had to an in-house ad-maker.

Scavino’s willingness to take on other people’s online grunt work made him indispensable. Early in the primary, Trump’s son-in-law, Jared Kushner, argued that Facebook was much more powerful than Trump’s preferred platform, Twitter.

“Every Facebook user is probably worth 10 to 12 times more than one of your Twitter followers,” Kushner told him. “And, look, I think your Facebook page is totally under-utilised.” The candidate responded: “Congratulations, then — you’re now in charge of my Facebook.” Kushner turned around and handed over that job to Scavino.

Even as Scavino’s deployment of campaign imagery onto Facebook helped accelerate the Trump train, it was Twitter, with its visceral impact, that remained Trump’s abiding love.

“Somebody said I’m the Ernest Hemingway of 140 characters,” he crowed during an event in South Carolina in November, 2015. (The “somebody” was most likely one of his employees.)

On his plane or in limousines, he would dictate tweets for Scavino to post. Others, including Scavino, would goad Trump with their own suggestions. (Hope Hicks would supply the choicest put-downs, recalls a former campaign official: “She’d have absolute daggers.”)

Trump would give his missive a final read to make sure that it had not been watered-down, and Scavino would hit ‘Tweet’. Now and again, Trump would enlist Scavino — whose followers today exceed 475,000 — to act as a proxy, attacking the campaign’s enemies from his own account.

At other times, Scavino took the initiative himself. Before long, the personal feed that had once been a totem of cornball folksiness included harsh attacks on Megyn Kelly, ‘Lyin’ Ted’ Cruz, and other perceived antagonists.

In March, 2016, Scavino retweeted a conspiracy video purporting to demonstrate that Cruz was having an affair with a former aide, Amanda Carpenter. Carpenter, who is married with children, went on the air and heatedly denied any impropriety. She also condemned Scavino by name, calling his attack a “smear job.”

“It was a campaign, and they fight dirty, and they didn’t mind if I was collateral damage in the process,” Carpenter told me. “And they won. And no consequences. What Scavino did to me, and what he still does to others, would get any other professional fired. In Trump’s universe, it’s a qualification.

“A willingness to engage in lies and smears, on behalf of Donald Trump, is a sign of loyalty that Trump treasures.”

“It’s so great that I have Twitter now, because I can knock the crap out of people,” Donald Trump told me one afternoon in late March, 2016, at his South Florida country club, Mar-a-Lago. “I have my own printing press now!” he added, with Falstaffian relish.

When President @realDonaldTrump announced that it is time to officially recognize Jerusalem as the capital of Israel, he fulfilled another campaign promise, in addition to those that go back 25 years.... pic.twitter.com/P7M2dEx2qT

— Dan Scavino Jr.🇺🇸🦅 (@DanScavino) December 7, 2017

Still, nothing in Trump’s earliest social-media forays would prefigure the towering role that Twitter eventually played in his political branding.

Trump opened his @realDonaldTrump account in March, 2009, only to ignore it for the better part of two years. Giving in to the urging of his political advisers, Roger Stone and Sam Nunberg, Trump began to tweet about his hotel properties and his TV show.

Of course, at that point the microblogging platform played a marginal-at-best role in American political life, even less so in presidential politics. The then president, Barack Obama, was a reluctant pioneer.

Tweets from his @POTUS account would undergo a policy and legal vetting process, and it could sometimes take days or even weeks before they were finally posted.The thought of using Twitter as a political cudgel “would have been completely against our values,” says Macon Phillips, Obama’s first digital director. “I think I would have left. I think a lot of us would have.”

At the time he announced his candidacy, in the summer of 2015, Trump was unsure of the role Twitter would play in his campaign. His tweets seemed to demonstrate only the fundamental unseriousness of his presidential ambitions.

As the campaign wore on, however, the candidate’s online disparagements no longer suggested a man bent on self-immolation. Rather, they reinforced the campaign talking point that here, at long last, was an honest politician, who did not bother to conceal his lesser angels.

His incessant howling of personal grievance only helped to show that the aloof titan of Fifth Avenue, mythologised in The Apprentice, had a tender underbelly. In baring his smallness, the billionaire New York developer collapsed the differences between his gilded life and that of white Middle America.

Today, Trump has not so much drained Washington’s swamp as convulsed it with daily electroshocks of presidential id.

Journalists now routinely awaken to the sound of a notification on their smartphones, telling them that the president is already up and driving the news in 280-character gonzo fusillades.

A far more common spectacle today than a legislative signing ceremony is the image of House Speaker Paul Ryan facing the microphones and, with a mortician’s smile, trying to explain away his party leader’s latest tweet: “It’s what he does. We’ve kind of learned to live with it.” (Or maybe not: Ryan made it less than halfway through Trump’s first term before announcing his retirement from Congress.)

The question of whether Trump’s social media outbursts constitute actual news has been rendered moot by his front-page-worthy announcements on Twitter: that his secretary of Veterans Affairs has been replaced, that he considers his own attorney general “beleaguered,” that “trade wars are good,” that “DACA is dead.”

The Trump presidency’s defining feature — its resolute abnormality — is above all the handiwork of @realDonaldTrump. It therefore stands to reason that Trump’s most-valued aide is the one whose job description has no precedent.

Scavino’s importance to the president explains how he has survived a succession of internecine bloodlettings in the West Wing.

But it’s also the case that he is well-liked among his colleagues, several of whom offered to help me understand his intrinsic value.

One senior White House official told me that the president trusts Scavino on personnel decisions. “Dan’s a very good judge of people,” he told me.

When I asked if he could supply me with any examples of Scavino’s advice-giving, the official replied coolly: “Absolutely not.”

But one longtime friend of Scavino’s offered an illuminating analogy. “Golf is a sport of the least mistakes,” he said. “That’s how someone like Dan might float to the top — by not doing anything wrong.”

Summer 2005 #ThrowbackThursday pic.twitter.com/7G6NejGHqZ

— Dan Scavino Jr.🇺🇸🦅 (@DanScavino) April 13, 2018

One of Scavino’s main roles is the care and feeding of his boss’s ego. He has learned how to fend off any negativity with a ready supply of superlatives.

While Hope Hicks would inform Trump about how some matter might be playing in the mainstream media, Scavino, Hicks told me, would “tell him how things are playing with his people. That’s a gauge for him that the president takes seriously.”

Checking in with the base is as easy as looking at his phone. Scavino’s old friend offered an example: “Dan would scroll through his Twitter feed and if Franklin Graham says something particularly complimentary, he’ll say, ‘Look what Franklin Graham just wrote.’ Or if [CNN show host] Brian Stelter says something particularly stupid, he’ll run over and say, ‘Look what Fake News is doing.’ ”

More than anyone else in the White House, the director of social media spends his day online, monitoring the #MAGA congregation.

“Dan talks to the base more than anybody else after the president,” one senior White House official told me. “He’s the conductor of the Trump Train, and these people know he’s true blue, and he also knows all the influencers.” A year ago, the former chief strategist Steve Bannon shared a West Wing office with Scavino.

“He has his hands on the Pepes,” Bannon recalls, referring to the cartoon frog that serves as mascot to the alt-right. “He knew who the players were and who were not. He’d bring me Cernovich — I didn’t know who Cernovich was until Scavino told me.” Bannon was referring to the alt-right blogger Mike Cernovich, who has frequently promoted debunked and scurrilous conspiracy theories.

When I asked Cernovich about his relationship with Scavino, he claimed they had none.

“No, never met him, never emailed with him, never D.M.’ed with him, and I don’t think he’s ever tweeted at me,” Cernovich said. In fact, by Cernovich’s standards, the Trump social media director was something of a lightweight. “Scavino’s not an ideologue,” he said disapprovingly.

“I don’t think he wakes up and says, ‘Holy hell, I want to break things today — who do I go after?’ It’s more, ‘I like my job and the Trump family.’ ” Still, Cernovich acknowledged that Scavino had most likely served as a conduit between the alt-right and Trump, if only through his eagerness to bring passionate fans to his boss’s attention.

Since arriving in Washington, Scavino has kept attacking President Trump’s opponents — Nancy Pelosi, Bill Kristol, Kathy Griffin — from his own Twitter account.

Last April, he went after Justin Amash, a Republican congressman from Michigan and frequent critic of Trump. Calling Amash “a big liability,” Scavino’s tweet urged, “#TrumpTrain, defeat him in primary.” Not easily intimidated, Amash replied, “Bring it on.”

But what instead was brought on was an investigation by the Office of Special Counsel, which concluded that Scavino had violated the Hatch Act, the law that forbids engaging in political activity while acting in your capacity as a government employee. On June 5, the O.S.C. disclosed that it had put Scavino on notice.

Though its statement made clear that future violations could result in harsher punishment, it neglected to say that only one individual could mete out that punishment: the president of the United States.

But the full extent of Scavino’s role in Trump’s Twitter regimen has never been fully disclosed. White House officials initially maintained to me that he only typed and posted verbatim what Trump dictated to him, while occasionally contributing anodyne tweets relating to the president’s schedule.

Somewhat begrudgingly, one senior official did not deny that Scavino also sometimes corrected Trump’s spelling errors. But the Knight Institute lawsuit had named Scavino, Hicks, and Sanders, because, as communications staff members, they are likely to “suggest content” for Trump’s tweets, just as Trump’s subordinates did during the campaign.

In particular, said one individual who witnessed this interactivity on the campaign trail and another who saw it in the White House, Scavino frequently supplied the litany of details in Trump’s tweets about, say, claims of ‘Crooked Hillary’s’ various malfeasances or of the FBI’s corrupt activity.

“Fifty percent of the time, Trump is ripping these out himself, and 50 percent is going to Scavino,” one of them told me. Evidence of Scavino’s participation in Trump’s tweets emerged last autumn.

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On the morning of October 4, Scavino posted to his own account one of the social media director’s usual rants against the media: “NBC news is #FakeNews and more dishonest than even CNN. They are a disgrace to good reporting. No wonder their news ratings are way down!”

One minute later, the identical message was posted on his boss’s account as an original Trump tweet. Scavino hastily deleted his first tweet, but not before eagle-eyed users took screen shots.

None of this should be so controversial, of course. No-one believes that Trump writes his speeches any more than they believe he wrote The Art of the Deal. Only a fool would suggest that his tweets represent the essence of someone other than Donald J. Trump.

All the same, my suggestion to a senior White House official that Trump might have some help in producing his mini-masterpieces was met with heated indignation. I was insulting the president’s capabilities. I was engaging in rank speculation. I was rewriting American history.

Still, the White House official did not once state that Trump was the sole author of every word of his tweets.

And Scavino, in the manner of any caddy who knows his place, continually avoided taking credit. He refused to answer even my basic question: What, exactly, did he do?

“When I was a first-year government student,” recalled the former Republican National Committee chairman and Bush strategist, Ken Mehlman, recently, “one of the first articles we had to read was Norman Mailer’s ‘Superman Comes to the Supermarket,’ which explained how J.F.K. was the man for the television age”.

It’s very possible that just as Kennedy possessed unique skills for that age, Donald Trump does for the social media age.”

With Twitter, Trump has subverted the news media, so-called allies, and the annoying constraints of human civility. Trump’s oft-repeated vow that he will never stop tweeting may count as his most rational act as president. It may also explain why Scavino could outlast everyone else in the White House.

He has outlasted Hope Hicks, who used to steam the president’s pants, and Keith Schiller, who — as I once witnessed backstage, at a campaign event in Buffalo — used to help apply hair product to the postmodern sculpture atop Trump’s head.

Managing Trump’s Twitter account, as it turns out, is an even more intimate act, something only Scavino has ever been trusted with. “I told Dan many times, during the campaign, ‘Once we win, you’ll have an entire team,’ ” Corey Lewandowski recalls.

“I’ve seen him many times since then, and it’s still a one-man operation.”

On a recent Monday in late March, I dropped by the West Wing to have one last in-person visit with some of Scavino’s colleagues and, hopefully, catch a glimpse of the social media director.

The evening before, Yashar Ali, of The Huffington Post, had broken the news that Scavino’s wife, Jennifer, had filed for divorce several weeks earlier.

I had heard rumors of the split from a former White House staff member, who, while praising Scavino’s crazed work ethic and fealty to Trump, casually added: “By the way, it also destroyed his marriage.”

Scavino had long-struggled to balance his ambitions with caring for his wife, who suffers from chronic Lyme disease.

That day in the West Wing, he was nowhere to be seen by the time I arrived. Scavino had boarded Air Force One with Trump and flown to Manchester to capture images of the president somberly proposing the death penalty for opioid dealers.

The personal toll of being Trump’s social media director may not end at Scavino’s marriage.

Last December, The Washington Post reported that an executive with Vkontakte, Russia’s version of Facebook, had twice emailed Scavino and Donald Trump Jr. during the presidential campaign, offering to promote Trump’s candidacy on the platform.

According to an email read to The Post, Scavino’s response to the American intermediary, Rob Goldstone, was effusive: “Please feel free to send me whatever you have. Thank you so much for looking out for Mr. Trump and his presidential campaign.”

A month after the Post story, Dianne Feinstein, the ranking Democratic member of the Senate Judiciary Committee, wrote Scavino a four-page letter. Noting media reports that Scavino is a “constant presence at Trump’s side,” Feinstein speculated that Scavino would know about the president’s decision to fire the FBI director, James Comey, as well as Russia’s interference in the 2016 election.

The senator, therefore, was writing “to request documents and to schedule an interview with you in January, 2018.”

Scavino retained the services of an attorney, who informed Feinstein that Trump’s social media director would not be responding to her requests. Without bipartisan prodding from the Judiciary Committee, and with Trump’s backing, he was free to ignore the senate inquiry.

Still, Scavino’s tweet from November, 2013, proved prescient in ways he had not expected: He would not be where he was today without @realDonaldTrump.

Robert Draper is a writer at large for The New York Times Magazine.