Donald Trump combines the instincts of a reality-TV star with the politics of a hundred-and-seventy-year-old nativist movement. PHOTOGRAPH BY SCOTT OLSON / GETTY

With Donald Trump ending 2015 well ahead in the Republican primary polls, the debate about what his candidacy represents is intensifying. Pointing to favorable remarks about Vladimir Putin that Trump made recently, Michael Gerson, a former speechwriter for President George W. Bush, said Sunday, on “Meet the Press,” “This is a man now flirting with authoritarianism. . . . This is a serious, serious matter.”

Some people have gone so far as to suggest that Trump, in whipping up popular resentments and stigmatizing immigrants and Muslims, is exhibiting Fascist tendencies. During the last Democratic debate, Martin O’Malley, the former governor of Maryland, said that America must never surrender its values “to the Fascist pleas of billionaires with big mouths.” Slate’s Jamelle Bouie has argued that “Fascist” is the label that best fits Trump, and the word has also cropped up in New Hampshire, where Trump is the front-runner. In a blog post, Jonathan P. Baird, an administrative law judge, noted that the candidate is popular with white supremacists and other hate groups, and wrote, “Trump is no conservative. He is not about conserving what is valuable in America’s laws and heritage. He has crossed enough lines to indicate he is something else altogether.”

That last statement is indisputable, but is “Fascism” the best way to describe the Trump phenomenon? I don’t think so. Originally used as a collective noun for the murderous, revolutionary hypernationalist movements that emerged in Europe from the embers of the First World War, the word is often employed today as a catch-all term of abuse for right-wing racists and rabble-rousers. Trump certainly qualifies as one of the latter, but calling him a Fascist serves to obscure rather than illuminate what he is really about.

Part of the problem is a definitional one. Even historians who have spent their lives studying Fascism can’t agree on what the word means. Were Adolf Hitler and Benito Mussolini Fascists? To be sure. What about Francisco Franco or António Salazar, or the colonels who seized power in Greece in 1967? Some historians would argue that these were old-fashioned military dictators who lacked the populist, revolutionary aspect of true Fascists. One voluminous collection of academic writings that I consulted over the Christmas break listed thirteen interpretations of Fascism. In a splendid piece of understatement, Stanley G. Payne, a historian at the University of Wisconsin-Madison and an expert on Franco’s Spain, remarked, “The absence of an empirical definition of what is meant by fascism has been an obstacle to conceptual clarification.”

But if historians of Fascism can’t write down on paper what it is, they can recognize it when they see it. And when Vox’s Dylan Matthews interviewed a number of them before Christmas, they agreed that Trumpism doesn’t meet the standard. Fascism, in its original form, had no time for parliamentary democracy, peace, or limited government. It exalted “direct democracy”—the incarnation of the popular will in a great leader—war, violence, and popular engagement in a totalitarian state. Trump, for all his bluster, hasn’t yet called for the repeal of the U.S. Constitution. He has expressed deep skepticism about U.S. military interventions overseas. And, despite his infamous comment that a Black Lives Matter protester at one of his rallies deserved to be roughed up, he hasn’t endorsed the sort of systematic violence that characterizes Fascist movements.

Plus—and this is something that Robert Paxton, of Columbia University, pointed out to Matthews—Trump is too much of a hedonistic individualist to endorse the sort of collective action and political mobilization that lay at the heart of Fascism. Far from creating an organized political movement that could overthrow the established order, Trump hasn’t even bothered, so far, to set up a decent get-out-the-vote operation in Iowa and New Hampshire—a failing that some political experts believe could be his undoing.

So, if Trump isn’t a Fascist, what is he? Something old and something new.

On the one hand, he is the latest representative of an anti-immigrant, nativist American tradition that dates back at least to the Know-Nothings of the eighteen-forties and eighteen-fifties. On the other hand, Trump is a twenty-first-century celebrity politician who ruthlessly exploits his fame and his insider knowledge of how the media works to maximum effect.

The Know-Nothings originated as secret societies of white Anglo-Saxon Protestants angered by an influx of immigrants, particularly Irish Roman Catholics who were crossing the Atlantic to flee poverty and find work in the rapidly industrializing U.S. economy. The Know-Nothings got their name because, when asked about their clandestine activities, they often said, “I know nothing.” Fearful of popery, liquor, and big-city political machines that harvested the votes of new arrivals, they called for restrictions on immigration, the closure of saloons, and a ban on foreign-born people holding public office. “Americans must rule America,” they said.

Prefiguring Trump’s remarks about Mexicans, the Know-Nothings also portrayed many immigrants as criminals. In his book “Nativism and Slavery: The Northern Know Nothings and the Politics of the 1850s,” the George Washington University historian Tyler Anbinder quoted contemporary newspaper articles that fixated on this subject. In Albany, a Know-Nothing paper called immigration “the chief source of crime in this country.” In Harrisburg, Pennsylvania, a like-minded publication said that crime had reached epidemic proportions, and that the perpetrators “are FOREIGNERS in nine cases out of ten.” In Cleveland, the Express identified one of the sources of the crime wave as the Roman Catholic confessional box, whose users “know no matter what the deed, they will be forgiven.”

In early 1854, Know-Nothing candidates won citywide offices in Boston, Philadelphia, and Washington, D.C. Coming together as a formal political organization for the first time, they adopted the name the American Party and swept statewide offices in Massachusetts, Maryland, and other states. In the run-up to the 1856 Presidential election, the Know-Nothings put together a Trumpian platform that demanded the repeal of naturalization laws, the banning of the foreign-born from public office, and the deportation of foreign-born paupers, including children.

As with the Trump phenomenon, economic concerns reinforced the Know-Nothing movement’s ethnic, religious, and cultural underpinnings. In Massachusetts, for instance, Know-Nothing politicians did best in industrial areas, where native workers were competing with Irish immigrants. With the rise of the Republican Party and the onset of the Civil War, the Know-Nothings entered a precipitous decline, but the prejudices and anxieties that motivated them never fully went away.

During the early decades of the twentieth century, another big wave of immigration, this one originating predominantly from southern and eastern Europe, produced a fresh burst of anti-immigrant feeling. Something similar has happened in the past couple of decades, following a surge in immigration from Latin America, the Caribbean, and Asia. With demographers projecting that white Americans will be a minority within a generation, nativist sentiment has returned, presenting Trump with his opportunity.

Since his non-campaign in 2012, when he publicly questioned whether President Obama was born in the United States, Trump has sought to fan fears that America is losing its heritage, and that the political establishment is complicit in a betrayal. The image of a big wall across the southern border is central to Trump’s campaign—not just in policy terms but also psychologically. It represents a physical manifestation of the desire to place a large stop sign before the onward march of history. As the campaign has progressed, Trump has added other elements that complement this proposal, such as a ban on Muslims entering the United States. His message may not be coherent, but it is consistent.