McMullin is not entirely comfortable with this newfound notoriety. Trim and neatly dressed, with a shaved head and a face composed of generic white-guy features, he doesn’t naturally stand out in crowds (an advantage, no doubt, in his undercover life). But in Donald Trump’s Washington, establishments like the Four Seasons are often teeming with partisans and loyalists who view McMullin as something between a nuisance and a menace. More than once as we ate, I caught him scanning the perimeters of the steak house, as though still on the lookout for adversaries.

“Sometimes,” he told me, “I will wear what at the agency we would call a ‘light disguise’ when I go out in public—like a hat and glasses.” But these days, he said, “my CIA tricks aren’t working. Maybe I’ve got to pull out one of my masks.”

The first time I met McMullin, last summer, he emanated a certain Mr. Smith Goes to Washington quality. Just a few hours after he had declared his candidacy for president—an announcement to which America responded with a resounding Huh?—we sat at a hotel bar in Midtown Manhattan, while a TV mounted above us periodically flashed images of his face. He seemed slightly overwhelmed, and though he tried not to look, he couldn’t help himself.

As a campaign neophyte with no national profile, McMullin knew he wasn’t the ideal man for the job he was taking on. For weeks, he had been among a contingent of conservatives seeking to recruit a better-known Republican to stand up and challenge Trump with an independent candidacy. But the effort proved futile. Conservative opposition was crumbling, and party leaders were swiftly falling in line behind their nominee. McMullin realized that no one else was going to step up, so he entered the race, holding out hope that principled Republican leaders would eventually join his cause. “It’s never too late to do the right thing,” he told me then, wide-eyed and dutiful-sounding.

McMullin headquartered his campaign in Utah—his birthplace, and a deep-red state where polls showed overwhelming dissatisfaction with the major-party nominees—and got to work giving stump speeches that blended the unbridled idealism of a West Wing episode with the unremarkable delivery of a high-school social-studies teacher. His optimistic calls for a “new conservative movement” untainted by Trumpism caught on in Utah, where he ended up winning more than 20 percent of the vote. But endorsements from courageous conservative leaders never materialized in any significant number—and with no serious financial backing, he struggled to compete elsewhere.

Since the election, McMullin has emerged as an even more strident, and high-profile, Trump adversary. He spends less time than he once did fretting about Trump’s corruption of Republicanism, and more time making the case that his presidency constitutes a national emergency. At the core of McMullin’s argument is a belief that America has elected an unambiguous authoritarian to the Oval Office.