Ruth Ben-Ghiat, an American-born professor of Italian history at New York University, specializes in male menace. What interests her is the manufactured drama of world-historical strongmen—their mannerisms, speech patterns, stagecraft, and mythomania. Late last year, Ben-Ghiat had just published a book called “Italian Fascism’s Empire Cinema,” about the years of Benito Mussolini, when another spectacle wrested her attention. One of the candidates for the American Presidency was looking a lot like her principal academic subject. As President Obama put it, the United States now had its own “homegrown authoritarian.”

Earlier this week, Ben-Ghiat sat at a table in her office, at N.Y.U.’s Casa Italiana, on Twelfth Street, inspecting two signatures on the screen of her laptop. One of them belonged to Donald Trump, the other to Mussolini. The scrawls—loopy, cursive, steepled—looked so similar that they seemed to blur together. Ben-Ghiat, who wore a gray sweater and dark skirt, is gracefully soft-spoken, her manner reserved. “I’m interested in how their language and writing are a kind of emanation of their bodies,” she said.

When Mussolini was a Socialist, he wrote his name as “Benito Mussolini.” “Then he dropped the Benito,” Ben Ghiat said. “He even had his stage name, which was Il Duce.” Trump also likes talking about himself in the third person. “He’s selling his product, which is himself,” she said. It’s a cult of personality peddled as good business. During the primaries, he recited a loyalty pledge in which he led his supporters in a promise to vote for him. (“I do solemnly swear that I—no matter how I feel, no matter what the conditions, if there’s hurricanes or whatever—will vote . . . for Donald J. Trump for President.”) While administering the oath, he raised his arm before the crowds in a quasi-Fascist salute. (“I mean, we’re having such a good time,” Trump said later. “Sometimes we do it for fun, and they start screaming at me, ‘Do the swearing! Do the swearing!’ ”)

“There’s this whole political theatre that they stage,” Ben-Ghiat said of both leaders. She called up a photo from a folder of images on her laptop, material from a PowerPoint she delivered at a recent seminar on the election. In the picture, Trump is walking through a rolling mist, from darkness to light, to accept the nomination at the Republican National Convention. “They have this hunger for approval. But their personas are created by the symbiosis with the crowd. They need the crowd to consolidate their personalities.” She has a theory about Trump’s manic sniffing throughout the debates: with the crowd silent, he was unmoored and defensive; he had no way to channel his nerves.

Ben-Ghiat grew up in the Pacific Palisades in the nineteen-seventies, at a time when the memory of exiled German émigrés, in flight from Nazism, was still fresh. “I had to think about what happened when dictatorship comes in,” she said. “Who stays, who leaves.” A trip to Rome after college led her to think about Mussolini, whose power was defined by a special sort of pageantry: he was a self-styled outsider who railed against the political system, but also managed to lull the establishment into acquiescence. Six months before taking over as Prime Minister, Mussolini famously asked, “Does Fascism aim at restoring the State, or subverting it? Is it order or disorder?”

“These people are mass marketers. They pick up what’s in the air,” Ben-Ghiat said. The film reel was to Mussolini as Twitter is to Trump. “They give the impression of talking directly to the people,” she said. They can be portentous and relentlessly self-assertive. In a way, authoritarians have to be, Ben-Ghiat explained, since they’re selling a paradox: a savior fashioned as the truest, most authentic expression of the masses. Trump summed it up baldly at the Convention: “I am your voice. I alone can fix it.” The authoritarian makes the contradiction fall away, like an optical illusion.

Authoritarians have a preoccupation with luxury, Ben-Ghiat said. “Steak is the everyman’s idea of luxury.” Photograph Courtesy Business Wire Photograph Courtesy Business Wire

This also explains authoritarians’ preoccupation with luxury. “They have to be populists, but they also have to be above it all,” Ben-Ghiat said. “Take Putin and his Apple Watch.” Last year, a jewelry brand named Caviar unveiled a limited-edition, gold-encrusted Apple Watch with an engraving of Putin’s signature. Ben-Ghiat clicked through more images until she came to a photograph of Trump, in his trademark boxy suit, leaning over a steak. She noted his hand, with thumb and index finger cocked, pointing at the meat. “Steak is the everyman’s idea of luxury,” she said.

To study authoritarianism is to study the male body in motion. Mussolini put his hands on his hips, thrust his chest, jutted his lower jaw. Trump, likewise, bobs and fidgets around the microphone. When under pressure or scrutiny, he pouts or rolls his eyes sarcastically. At some rallies, he’s thrown the pages of a printed speech off the lectern to show he can’t be scripted, and has explicitly disparaged the teleprompter as an affront to his style. “It’s all about showing that he cannot be contained,” Ben-Ghiat told me. “At the beginning, people loved going to the show of Donald Trump. You didn’t know what he was going to do or say. It was the same with Mussolini. He would insult people in a humorous way. You didn’t know what gestures he would make.”

Ben-Ghiat has been broadening her studies ever since the primaries, and is now considering a book-length examination of strongmen, from Mussolini to Trump, with stops in Franco’s Spain, Erdoğan’s Turkey, and Qaddafi’s Libya. In the speech of Mussolini, Putin, Trump, and also Berlusconi, Ben-Ghiat notes a pattern: they are at once transparent about their intentions and masters of innuendo. “Trump trails off. He uses ellipses and coded language. He lets his listeners fill in what they want.” When Trump seemed to suggest that gun owners should deal with Hillary Clinton themselves, or when he talked about needing to “watch” certain communities out to steal the vote on Election Day, his statements were more powerful for their ambiguity. “It’s all about letting listeners convince and mislead themselves,” she said. Still, she added, these men tend to do as they say. In Mussolini’s case, it took the assassination of a Socialist opponent, in 1924, to shock the political scene into belated awareness of who, exactly, was in its midst. When Il Duce claimed that he would further “clarify” matters, his audience understood that “clarification” was a synonym for violence. Ben-Ghiat has been thinking about these words as Election Day nears. On the stump, Trump keeps saying that order will be restored on January 20th, as soon as he takes office. “He means everything he says,” Ben-Ghiat said. “Authoritarians never pivot.”