What is fascism? A look at the term being hurled at Donald Trump

Former President Donald Trump has recently been called a "fascist" by his former chief of staff, John Kelly, his opponent, Vice President Kamala Harris, and leading historian Robert Paxton.

Kelly, a former four-star Marine general and former chief of staff to Trump, hammered his old boss as a "fascist" in a New York Times interview.

"Well, looking at the definition of fascism: It's a far-right authoritarian, ultranationalist political ideology and movement characterized by a dictatorial leader, centralized autocracy, militarism, forcible suppression of opposition, belief in a natural social hierarchy," Kelly told The Times.

"So, certainly, in my experience, those are the kinds of things that he thinks would work better in terms of running America," he added.

But for scholars who've long studied fascism, defining fascism isn't so simple.

"We're not just debating whether or not Trump fits that definition; we are not agreeing on what that definition is," Sheri Berman, a political science professor at Barnard College, Columbia University, told ABC News in an interview.

There is no scholarly consensus on the term, according to both Berman and Mark Bray, a political scientist from Rutgers University. This is, in part, because fascists historically have not been tied to "rational consistency," Bray said, pointing to Italian dictator Benito Mussolini and Nazi Germany dictator Adolf Hitler whose policy positions changed on a variety of occasions.

To Berman, fascists are totalitarian with the goal of not just controlling politics, but reshaping society and controlling the economy.

"These were inherently violent movements," Berman said. "They didn't just use violence as a means right to conquer power or to go out and conquer other parts of the world, but they believed violence is an end in and of itself. It had this kind of cleansing and empowering aspect that would again contribute to sort of changing society, changing the individuals that compose society."

RELATED: John Kelly comes out swinging against Trump, says he fits 'fascist' definition

Fascism, according to Bray, is rooted in the desire "to return to an imaginary past where natural hierarchies were respected, hierarchies around nationalism or gender or race, and it aims to use mass popular politics to get there with a focus on violence" to rid society on its undesirable elements.

Among historians and political scientists, it's a toss-up as to whether they believe Trump fully fits the bill.

In a New York Times interview published on Oct. 23, Paxton said the Jan. 6 Capitol insurrection eliminated his reservations about calling Trump a fascist.

However, he said focusing on the leader of a movement and not the mass from which it has flourished is a mistake.

"The Trump phenomenon looks like it has a much more solid social base," as Hitler and Mussolini were appointed and not elected officials, Paxton told The Times. "Which neither Hitler nor Mussolini would have had."

Bray believes there's a distinction between Trump and "Trumpism" as a political movement and the similarities to fascism.

"I would call Trumpism unequivocally a kind of 21st century American fascism," said Bray, arguing that Trump's most ardent fans may see themselves as "victims who need to transcend the limit of democratic politics ... (using) redemptive violence to take their country or their nation or their society back."

Bray believes Trump's relationship with his supporters has radically affected his policy: "I think that those initiatives are coming stronger and are more heartfelt from the base of Trumpism at the state level, at the county level."

Bray stops short of calling Trump a fascist in the traditional sense, seeing as he does not embrace all of the ideals of a historical fascist. For example, fascists have historically rejected free market capitalism, unlike Trump.

Instead, Bray calls Trump "fascistic" -- "I think the term fascist suggests that he's more of an ideologue of this than I think he really is," Bray said.

Berman does not pin Trump as a fascist, calling him instead an "anti-democratic" and "authoritarian." However, she added that this does not mean his encouragement of violence -- like his comments on using National Guard troops to go after "radical left lunatics" or nativist rhetoric and plans to deport millions of undocumented immigrants -- does not align with fascist tendencies.

The ongoing debate also questions whether it's helpful to use the term when discussing Trump and modern politics.

Berman argues that terms should "help you understand the phenomenon that is being described," and the confusion and mystification around the term has only clouded its impact.

"The reason why I prefer to stress his kind of anti-democratic and illiberal aspects is ... it gives citizens something very concrete to focus on," Berman said, pointing to Trump's specific policies and plans. "It helps them understand what the danger is when you see someone as a fascist."

Paxton agreed with this sentiment in his interview with the NYT, arguing that the overuse cheapens the meaning -- "I think there are ways of being more explicit about the specific danger Trump represents," he said.

In an Oct. 23 town hall on CNN, Harris called Trump a "fascist," and said Kelly's criticisms of him are an effort to put out a "911 call to the American people."

Later in the town hall, Harris outright called Trump a "fascist" while answering a question on Palestinian civilians being killed in Gaza, (which Harris called "unconscionable") and voters choosing to stay home or protest vote over the war, arguing that many are not single-issue voters.

"But I also do know that for many people who care about this issue, they also care about bringing down the price of groceries," Harris argued. "They also care about our democracy and not having a president of the United States who admires dictators and is a fascist."

On Truth Social, Trump slammed Harris for her comments, instead calling Harris a "threat to democracy. However, he falsely claimed she referred to him as Hitler.

"Comrade Kamala Harris sees that she is losing, and losing badly, especially after stealing the Race from Crooked Joe Biden, so now she is increasingly raising her rhetoric, going so far as to call me Adolf Hitler, and anything else that comes to her warped mind," said Trump. "She is a Threat to Democracy, and not fit to be President of the United States - And her Polling so indicates!"

ABC News has reached out to the Trump campaign for further comment.

ABC News' Soo Rin Kim contributed to this report.