But Trump himself prefers to keep his options open, and his allegiances can be quite malleable. His tendency to wash his hands of ties is widely noted, running all the way back to the 1980s, when, according to a secretary employed by Cohn — the mentor whose loyalty Trump so praised — Trump responded to Cohn’s learning of his own H.I.V. infection by severing professional ties. Trump’s ideology is just as famously flexible. Sixteen years before he ran for president as a Republican, he nearly ran under the flag of Ross Perot’s Reform Party, telling Larry King that his desired vice-presidential pick was Oprah Winfrey. He may vow to end DACA in one conversation and to work to salvage it in another. There’s no clear pattern to his changing sympathies, which means that when he demands your loyalty, you cannot quite know what it is that you’re signing up for. You can’t even count on his disloyalty: In August, he cashed in a good deal of political capital to extend a pardon to Joe Arpaio, the former sheriff of Maricopa County, Ariz. — partly out of what seemed, to genuinely surprised observers, like an earnest sense of obligation to an ally.

If this is a version of loyalty, it’s loyalty of a low order — fragile, transactional and much closer to simple fealty. It fails Royce’s expectation that real loyalty be based in “willingness,” rather than in fear. It’s the kind that scaffolds autocratic governments, in which the ruler’s power is always dependent on a network of unstable personal alliances — and all hints of potential disloyalty must be flamboyantly purged.

The core contention of Trump’s campaign, oddly enough, was that he was the only loyal candidate in the field — the only one powerful, wealthy and independent enough to act on behalf of the American hoi polloi, rather than in his own interests or those of his donors. “I didn’t need to do this,” he told a news conference in Florida, alluding to his already sizable fortune. One ad promised to replace the “corrupt establishment” who usually held power “with a new government controlled by you, the American people.”

There’s an important claim at the heart of this kind of populism — that the failings of government aren’t a problem of policy, but a problem of allegiance. It isn’t that politicians are incapable of improving the lives of ordinary Americans; it’s that they choose not to, because their true interests lie elsewhere. This is the genius of a slogan like “Make America Great Again,” with its implication that other politicians have a more noncommittal attitude concerning the nation’s potential greatness. By signaling, over and over, that his loyalties lay somewhere outside the norm, Trump could build an ad hoc coalition of people who felt ill served by the normal political class, for almost any reason at all — an effect only reinforced by every attack on his campaign. When Hillary Clinton referred to many of his supporters as “deplorables,” she offered them the gift of a name — along with hard evidence that Trump was, in fact, their only loyal protector, and the only one interested in their opinions and grievances.