To support The Atlantic’s journalism, please consider subscribing today.

Rhetoric has a history. The words democracy and tyranny were debated in ancient Greece; the phrase separation of powers became important in the 17th and 18th centuries. The word vermin, as a political term, dates from the 1930s and ’40s, when both fascists and communists liked to describe their political enemies as vermin, parasites, and blood infections, as well as insects, weeds, dirt, and animals. The term has been revived and reanimated, in an American presidential campaign, with Donald Trump’s description of his opponents as “radical-left thugs” who “live like vermin.”

This language isn’t merely ugly or repellant: These words belong to a particular tradition. Adolf Hitler used these kinds of terms often. In 1938, he praised his compatriots who had helped “cleanse Germany of all those parasites who drank at the well of the despair of the Fatherland and the People.” In occupied Warsaw, a 1941 poster displayed a drawing of a louse with a caricature of a Jewish face. The slogan: “Jews are lice: they cause typhus.” Germans, by contrast, were clean, pure, healthy, and vermin free. Hitler once described the Nazi flag as “the victorious sign of freedom and the purity of our blood.”

[Peter Wehner: Have you listened lately to what Trump is saying?]

Stalin used the same kind of language at about the same time. He called his opponents the “enemies of the people,” implying that they were not citizens and that they enjoyed no rights. He portrayed them as vermin, pollution, filth that had to be “subjected to ongoing purification,” and he inspired his fellow communists to employ similar rhetoric. In my files, I have the notes from a 1955 meeting of the leaders of the Stasi, the East German secret police, during which one of them called for a struggle against “vermin activities” (there is, inevitably, a German word for this: Schädlingstätigkeiten), by which he meant the purge and arrest of the regime’s critics. In this same era, the Stasi forcibly moved suspicious people away from the border with West Germany, a project nicknamed “Operation Vermin.”

This kind of language was not limited to Europe. Mao Zedong also described his political opponents as “poisonous weeds.” Pol Pot spoke of “cleansing” hundreds of thousands of his compatriots, so that Cambodia would be “purified.”

In each of these very different societies, the purpose of this kind of rhetoric was the same. If you connect your opponents with disease, illness, and poisoned blood, if you dehumanize them as insects or animals, if you speak of squashing them or cleansing them as if they were pests or bacteria, then you can much more easily arrest them, deprive them of rights, exclude them, or even kill them. If they are parasites, they aren’t human. If they are vermin, they don’t get to enjoy freedom of speech, or freedoms of any kind. And if you squash them, you won’t be held accountable.

Until recently, this kind of language was not a normal part of American presidential politics. Even George Wallace’s notorious, racist, neo-Confederate 1963 speech, his inaugural speech as Alabama governor and the prelude to his first presidential campaign, avoided such language. Wallace called for “segregation today, segregation tomorrow, segregation forever.” But he did not speak of his political opponents as “vermin” or talk about them poisoning the nation’s blood. Franklin Delano Roosevelt’s Executive Order 9066, which ordered Japanese Americans into internment camps following the outbreak of World War II, spoke of “alien enemies” but not parasites.

[Read: Trump isn’t bluffing]

In the 2024 campaign, that line has been crossed. Trump blurs the distinction between illegal immigrants and legal immigrants—the latter including his wife, his late ex-wife, the in-laws of his running mate, and many others. He has said of immigrants, “They’re poisoning the blood of our country” and “They’re destroying the blood of our country.” He has claimed that many have “bad genes.” He has also been more explicit: “They’re not humans; they’re animals”; they are “cold-blooded killers.” He refers more broadly to his opponents—American citizens, some of whom are elected officials—as “the enemy from within … sick people, radical-left lunatics.” Not only do they have no rights; they should be “handled by,” he has said, “if necessary, National Guard, or if really necessary, by the military.”

In using this language, Trump knows exactly what he is doing. He understands which era and what kind of politics this language evokes. “I haven’t read Mein Kampf,” he declared, unprovoked, during one rally—an admission that he knows what Hitler’s manifesto contains, whether or not he has actually read it. “If you don’t use certain rhetoric,” he told an interviewer, “if you don’t use certain words, and maybe they’re not very nice words, nothing will happen.”

His talk of mass deportation is equally calculating. When he suggests that he would target both legal and illegal immigrants, or use the military arbitrarily against U.S. citizens, he does so knowing that past dictatorships have used public displays of violence to build popular support. By calling for mass violence, he hints at his admiration for these dictatorships but also demonstrates disdain for the rule of law and prepares his followers to accept the idea that his regime could, like its predecessors, break the law with impunity.

These are not jokes, and Trump is not laughing. Nor are the people around him. Delegates at the Republican National Convention held up prefabricated signs: Mass Deportation Now. Just this week, when Trump was swaying to music at a surreal rally, he did so in front of a huge slogan: Trump Was Right About Everything. This is language borrowed directly from Benito Mussolini, the Italian fascist. Soon after the rally, the scholar Ruth Ben-Ghiat posted a photograph of a building in Mussolini’s Italy displaying his slogan: Mussolini Is Always Right.

These phrases have not been put on posters and banners at random in the final weeks of an American election season. With less than three weeks left to go, most candidates would be fighting for the middle ground, for the swing voters. Trump is doing the exact opposite. Why? There can be only one answer: because he and his campaign team believe that by using the tactics of the 1930s, they can win. The deliberate dehumanization of whole groups of people; the references to police, to violence, to the “bloodbath” that Trump has said will unfold if he doesn’t win; the cultivation of hatred not only against immigrants but also against political opponents—none of this has been used successfully in modern American politics.

But neither has this rhetoric been tried in modern American politics. Several generations of American politicians have assumed that American voters, most of whom learned to pledge allegiance to the flag in school, grew up with the rule of law, and have never experienced occupation or invasion, would be resistant to this kind of language and imagery. Trump is gambling—knowingly and cynically—that we are not.