On a late January afternoon, as press secretary Sean Spicer walked into the White House media briefing room, a tall, thin, bespectacled man poked his head in the doorway for a moment before turning around and heading back into the West Wing. Later that week, at another briefing, the man stayed longer, standing in the corner behind the podium, out of view of the array of television cameras.

The reporters peppering Spicer with questions were unlikely to know it, but the wallflower watching over the proceedings happened to be the leading conservative intellectual to argue for the election of Donald Trump. His pseudonymous essays during the campaign sparked more discussion—and disputation—among thinkers on the right than just about anyone else's. Rush Limbaugh spent hours on his radio show promoting what he hailed as the writer's "shaming" of the Never Trump conservatives. Leading conservative opponents of Trump, like New York Times columnist Ross Douthat, National Review's Jonah Goldberg, and Washington Post columnist Michael Gerson, published critical responses to his most widely read essay. The writer even granted a postelection interview to the New Yorker, on the condition that his real identity not be revealed. The magazine described him as among those trying "to build a governing ideology" around Trump.

Now he's helping to implement that governing ideology directly. The writer is a senior national-security official in the Trump White House, nearly a decade after serving in a similar role for George W. Bush. His unmasking ends one of the remaining mysteries of last year's crazy and unpredictable election.

The enigmatic writer's real name is Michael Anton, and he's a fast-talking 47-year-old intellectual who, unlike most of his colleagues, can readily quote Roman histories and Renaissance thinkers. But readers knew him throughout 2016 as Publius Decius Mus, first at a now-defunct website called the Journal of American Greatness and later in the online pages of the Claremont Review of Books. As Decius, Anton insisted that electing Trump and implementing Trumpism was the best and only way to stave off American decline—making a cerebral case to make America great again.

At the center of Anton's/Decius's argument (distilled best in his September essay for the Claremont Review entitled "The Flight 93 Election") was the belief that the decline of the United States under the direction of the progressive left has been abetted by a bloated and lethargic conservative movement of "think-tanks, magazines, conferences, and fellowships" that exists to perpetuate the status quo. Conservative intellectuals had been living a contradiction, wrote Decius, decrying the decay of America's social, economic, and political traditions while offering nothing but tired ideas that tinkered on the margins of public policy—if they did anything at all. More nefariously, Decius suggested, professional conservative intellectuals were more motivated to preserve their own status (and steady stream of paychecks) than to reconsider their positions and ideological priors. His writing on this point was at once funny, clever, and vicious:

How have the last two decades worked out for you, personally? If you're a member or fellow-traveler of the Davos class, chances are: pretty well. If you're among the subspecies conservative intellectual or politician, you've accepted—perhaps not consciously, but unmistakably—your status on the roster of the Washington Generals of American politics. Your job is to show up and lose, but you are a necessary part of the show and you do get paid. To the extent that you are ever on the winning side of anything, it's as sophists who help the Davoisie oligarchy rationalize open borders, lower wages, outsourcing, de-industrialization, trade giveaways, and endless, pointless, winless war.

For Decius, the stakes for the 2016 election were civilizational, a choice between a continuation of corrupt republicanism in the service of progressive ideals and a disruption of that arc. Violence and battle are his preferred motifs: The left is looking to "crush" dissent; a Hillary Clinton presidency would have been "Russian Roulette with a semi-auto." The titular "Flight 93" refers to the hijacked plane on 9/11 that passengers heroically took back from terrorists and was his heavy-handed metaphor for the election. He even chose a martial nom de plume. In his History of Rome, Livy describes Publius Decius Mus as a Roman consul who rode to the front of his army in battle, sacrificing himself to save his men and Rome. Again, and to be clear, it's just a metaphor.

Anton/Decius viewed Trump as the only Republican willing and eager to sacrifice conservative pieties to save America. "Trump, alone among candidates for high office in this or in the last seven (at least) cycles, has stood up to say: I want to live. I want my party to live. I want my country to live. I want my people to live. I want to end the insanity," he wrote. But it's not just the poetry Decius finds compelling about Trump—he's a fan of the prose: "The truth is that Trump articulated, if incompletely and inconsistently, the right stances on the right issues—immigration, trade, and war—right from the beginning."

Anton wasn't always where Trump is on these issues, and he has the profile of exactly the type of movement conservative for which Trumpism has no use. He was inculcated in the Straussian conservative world of the Claremont Graduate School, reading—besides the late political philosopher Leo Strauss—ancient philosophy, modern political theory, and Machiavelli. (He married his interest in the Italian Renaissance writer with his passion for men's fashion in a 2006 book called The Suit, a word-for-word parody of The Prince also written under a pseudonym.)

After working as a speechwriter and press secretary for New York mayor Rudy Giuliani, he entered Bush's White House in 2001 as a communications aide for the National Security Council—a job that took on greater weight after 9/11. Anton was part of the team that made the case within the administration and to the public for invading Iraq—and he was enthusiastic about the war. That team** helped craft one of the more infamous sentences in a State of the Union address, from Bush's in 2003: "The British government has learned that Saddam Hussein recently sought significant quantities of uranium from Africa."

Those 16 words, which CIA director George Tenet later said "never should have been included" in the president's address, became a touchstone for those who contended the case for invading Iraq was trumped up. Decius doesn't mention the words or the arguments for the Iraq war in any of his writings, but he does state in his first essay for the Journal of American Greatness that the invasion "was a strategic and tactical blunder that destroyed a country (however badly governed), destabilized a region, and harmed American interests."

His evolution on the issue of Iraq is perhaps Anton's most notable shift, but it's not the only one informed by his experience as a member of the governing class he so artfully assailed as Decius. After leaving the Bush administration in 2005, Anton was a speechwriter for Rupert Murdoch at the media conglomerate News Corporation, then the director of communications at megabank Citigroup. For the last year and a half, he's been a managing director at the investment firm BlackRock. With that résumé, it's no wonder the man who referred to the "Davos class" as a "junta" and wrote that it would "be better for the nation to divide up more equitably a slightly smaller pie than to add one extra slice" chose to write under a pseudonym. Anton would no doubt happily accept that he is a "traitor to his class," which is what his Journal of American Greatness compatriot Julius Krein called Donald Trump in these pages. (Anton himself has contributed many pieces to THE WEEKLY STANDARD and its website, as recently as last year.)

Anton may also be a traitor to his class of conservative intellectuals, though his writings on Trump rejected by the Claremont Review of Books in early 2016 eventually found their home there by the end of the election. More consequential, in his new position as senior director of strategic communications at the National Security Council, he brings his brand of intellectual Trumpism right to the White House and the locus of power. The job was initially given to Monica Crowley, the writer and television pundit, with the intention that she be a public face for the Trump White House on national-security issues. But Crowley was forced to withdraw just days before Trump was inaugurated after reports revealed she had plagiarized her last book and her Ph.D. thesis. Anton's role will likely involve less camera time and more shaping of the White House's national-security message behind the scenes.

In "The Flight 93 Election," Decius considered the 2016 election as a game of Russian roulette for conservatives. A President Clinton would all but assure annihilation of everything they hold dear. "With Trump, at least you can spin the cylinder and take your chances," he wrote. Decius's spin turned out well for him—now he's at the front of the battle line, saving Rome.

*A version of this article appears in The Weekly Standard issue of February 13, 2017.

**Correction: This article imprecisely stated Anton himself had crafted the sentence about Saddam seeking uranium from Africa. It was the National Security Council team, of which he was a part, that contributed to including the sentence in Bush's speech.