He’s been compared to Hitler. And also Voldemort. And also Mussolini, and an African dictator, and Sanjaya, and Biff Tannen from Back to the Future, and, mainly for aesthetic purposes, an orangutan. And yet recently a new epithet has emerged to describe Donald J. Trump, one that aims in its way to combine all those other comparisons into a single, sweeping dismissal: “demagogue.” “Textbook Demagogue.” “American Demagogue.” “Thug demagogue.”

As an insult, certainly—as an implicit invalidation of one’s political rhetoric—“demagogue” is a very good word. It’s slightly gentler than “fascist” and slightly more dignified than “buffoon”; it’s extremely opinionated, and yet carries itself with the gravitas of informed objectivity. Uttered aloud—that evocative agog— it forces one’s mouth to gape appropriately. And while Trump is certainly not the only contemporary politician to be dismissed under its auspices (“Demagoguery 101,” Charles Krauthammer wrote of President Obama and his policies), no figure has so clearly deserved the word since Huey Long and Joe McCarthy and Pat Buchanan riled the former century. So deep has the impact of Trump’s fist-pounding rhetoric been that, at this point, there’s a metonymic circularity to the whole thing. The Economist recently published an article titled “The Art of the Demagogue.” It did not need to clarify who it was about.

But what, actually, are people accusing Trump of when they accuse him of demagoguery? It’s not simply Biffery or buffoonery or baboonery; it’s something more contextualized. More systemic. More dangerous. To call Trump a “demagogue” is to do two things at once: to dismiss him as a political candidate and amplify him as a political threat. That is appropriate, because the key thing about demagogues, historically, is that they have been people who, by way of their very popularity, threaten the populace. They undermine the stability of a “by the people” form of government particularly by turning “the people” against each other. They represent a danger not just to electoral outcomes or political parties, but to democracy itself.

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“Demagogue,” as a term—“demos,” the people, and “agogos,” leader—is pretty much as old as democracy is. It was born, like so many others of our most effective insults, in ancient Athens. And despite its anodyne etymology, it almost instantly took on a negative connotation: In Greece, the demagogue was not just a leader of people, but a leader who led, specifically, by bullying/cajoling/converting charisma into influence. He was a populist who appealed, in particular, to the lower classes. As Aristotle wrote of Cleon, a tanner, “He was the first who shouted on the public platform, who used abusive language and who spoke with his cloak girt around him, while all the others used to speak in proper dress and manner.”

Aristotle described Cleon and his fellow platform-shouters as “gadflies,” which captured not just how annoying he found them to be, but also how destructive: When large animals are pestered into a frenzy, one thing that can result is a stampede that sends them, collectively, over a cliff. For Aristotle, demagogues—people who used democracy, he felt, against itself—were potential threats to the political system he and his fellow democracy-designers were trying to build. “Revolutions in democracies,” he declared, “are generally caused by the intemperance of demagogues.”

The Athenian democracy did, in its way, survive. But its philosopher’s fear of demagogues, and of the vague threat they suggested of revolution from within, extended into the modern world. It is Charles I, arguing (unsuccessfully) for the monarchy and for his life in Eikon Basilike, who is generally credited with re-introducing the term into English. (Whereupon John Milton, as both an avid republican and perhaps an even more avid inventor of language, dismissed it as a “Goblin word,” sniffing: “The King by his leave cannot coine English as he could Money, to be current.”)

But while the word proved its utility as both a political description and an epithet, it also, thus anglicized, lost some of the Aristotelian certainty that had defined it in earlier ages. Latham’s A Dictionary of the English Language, a re-print of Doctor Johnson’s sweeping version from 1755, defines “demagogue” as “ringleader of the rabble” but also, secondarily, as a “popular and factious orator.” A New Dictionary of the English Language, published in 1867, lists “demagogue” as “a leader of the people,” but goes on to suggest that the term is “applied to a factious or seditious leader.” Trollope, in his 1855 novel The Warden, demurred: “Now I will not say that the archdeacon is strictly correct in stigmatizing John Bold as a demagogue, for I hardly know how extreme must be a man’s opinions before he can be justly so called.”

That muddled sense of demagoguery—extremity that is threatening both despite and because of its vagueness—continues today. (This despite efforts among academics to classify demagogues: Type I, Type II, and so on.) And it is enabled not just by TV and Twitter and a cultural environment that converts human charisma into mass media, but by our political system itself. As Michael Signer notes in Demagogue: The Fight to Save America From Its Own Worst Enemies: “Democracy—and any other system with an element of democracy—intrinsically creates an opening for a demagogue.”

Today, perhaps as a response to that vague but ongoing threat of media-driven menace, “demagogue” has become a term of last resort: a description—a deeply loaded epithet—that is summoned only when a particular politician or media figure or other modern people-leader has moved so far away from the mainstream that the Overton Window has receded well into the distance. It’s a word that doubles as a siren for a democratic system, directed at one person but implicating us all: Our house is on fire. It’s this sense that gave the phrase its shock value, and its lasting power, when H.L. Mencken dismissed Huey Long as “a backwoods demagogue.” And when Joe Kennedy decried Father Coughlin as “an out and out demagogue.” It is why American history, its terrain so widely populated with people who bluster and flatter and smarm and shout, has anointed so few actual “demagogues.”

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Which makes it telling, and significant, that the people who today are writing the rough draft of future histories are playing that trump card against one, yes, Donald Trump. You could dismiss those dismissals as misinformed, or melodramatic, or evidence that the Internet’s outrage machine has once again overridden nuance and/or rational thought. You could, too, point out the obvious: that there is an extent, inevitably, to which demagoguery is in the eye of the beholder. (Plutarch, in Theseus, wrote of Menestheus, who “sowed disturbance” among the “common people” by “telling them, that though they pleased themselves with the dream of liberty, in fact they were robbed of their country and religion”—a description that might also apply to a freedom fighter, or a revolutionary, or any other person whom history remembers as a “hero.”)

You could say, basically, that Trump’s popular reception has been making exceedingly clear what every “demagogue” will: that one person’s threat to democracy is another person’s populist hero.

And yet. Democracy, by its nature, allows for only so much relativism. At a certain point—that point traditionally being an election—the people will have to come to some kind of awkward agreement about who they are and what they want. At some point, too, they will have to decide what Trump is, and whether they can stomach what he claims to represent.

In the meantime, though, Trump embodies, with his pounding fist and his artilleried insults and his cheeky baseball cap, the uneasy compromise of the American experiment. He is a human distillation of the maxim that democracy “is a device that ensures we shall be governed no better than we deserve.” In all that, he may well represent just what Aristotle feared: democracy, feeding on itself. And thereby destroying itself. Which is a fear, it’s worth noting, shared by the Founders. As Alexander Hamilton, summoning his reading of history and human nature, warned: “Of those men who have overturned the liberty of republics, the greatest number have begun their career by playing an obsequious court to the people, commencing demagogues and ending tyrants.”