(CNN) Conservative warnings about Donald Trump have grown increasingly somber. At first he was just an entertainer; then he became a worrisome distraction, and soon, there was fear that he would permanently scar the reputation of the Republican Party.

But it was after Trump started calling for stronger surveillance of Muslim-Americans in the aftermath of the Paris terrorist attacks that a handful of conservatives ventured to call Trump's rhetoric something much more dangerous: fascism.

Since launching his campaign this summer, the billionaire real estate magnate has regularly deployed inflammatory rhetoric about immigrants -- particularly regarding Latinos -- and repeatedly raised the alarm about foreigners entering the country. That has escalated following the series of shooting rampages and explosions in Paris this month allegedly perpetrated by ISIS and amid a national debate over accepting Syrian refugees.

Trump is joined by his family as he is sworn in as President on January 20.

Trump is joined by his family as he is sworn in as President on January 20.

Trump walks on stage with his family after he was declared the election winner on November 9. "Ours was not a campaign, but rather, an incredible and great movement," he told his supporters in New York.

Trump walks on stage with his family after he was declared the election winner on November 9. "Ours was not a campaign, but rather, an incredible and great movement," he told his supporters in New York.

Trump apologizes in a video, posted to his Twitter account in October, for vulgar and sexually aggressive remarks he made a decade ago regarding women. "I said it, I was wrong and I apologize," Trump said, referring to lewd comments he made during a previously unaired taping of "Access Hollywood." Multiple Republican leaders rescinded their endorsements of Trump after the footage was released.

Trump faces Democratic nominee Hillary Clinton in the first presidential debate, which took place in Hempstead, New York, in September.

Trump delivers a speech at the Republican National Convention in July, accepting the party's nomination for President. "I have had a truly great life in business," he said. "But now, my sole and exclusive mission is to go to work for our country -- to go to work for you. It's time to deliver a victory for the American people."

Trump delivers a speech at the Republican National Convention in July, accepting the party's nomination for President. "I have had a truly great life in business," he said. "But now, my sole and exclusive mission is to go to work for our country -- to go to work for you. It's time to deliver a victory for the American people."

Trump speaks during a campaign event in Evansville, Indiana, on April 28. After Trump won the Indiana primary, his last two competitors dropped out of the GOP race.

Trump speaks during a campaign event in Evansville, Indiana, on April 28. After Trump won the Indiana primary, his last two competitors dropped out of the GOP race.

Trump -- flanked by U.S. Sens. Marco Rubio, left, and Ted Cruz -- speaks during a CNN debate in Miami on March 10. Trump dominated the GOP primaries and emerged as the presumptive nominee in May.

Trump -- flanked by U.S. Sens. Marco Rubio, left, and Ted Cruz -- speaks during a CNN debate in Miami on March 10. Trump dominated the GOP primaries and emerged as the presumptive nominee in May.

Trump speaks in Sarasota, Florida, after accepting the Statesman of the Year Award at the Sarasota GOP dinner in August 2012. It was shortly before the Republican National Convention in nearby Tampa.

Trump speaks in Sarasota, Florida, after accepting the Statesman of the Year Award at the Sarasota GOP dinner in August 2012. It was shortly before the Republican National Convention in nearby Tampa.

Trump poses with Miss Universe contestants in 2011. Trump had been executive producer of the Miss Universe, Miss USA and Miss Teen USA pageants since 1996.

Trump poses with Miss Universe contestants in 2011. Trump had been executive producer of the Miss Universe, Miss USA and Miss Teen USA pageants since 1996.

Trump appears on the set of "The Celebrity Apprentice" with two of his children -- Donald Jr. and Ivanka -- in 2009.

Trump appears on the set of "The Celebrity Apprentice" with two of his children -- Donald Jr. and Ivanka -- in 2009.

For "The Apprentice," Trump was honored with a star on the Hollywood Walk of Fame in January 2007.

For "The Apprentice," Trump was honored with a star on the Hollywood Walk of Fame in January 2007.

Trump wrestles with "Stone Cold" Steve Austin at WrestleMania in 2007. Trump has close ties with the WWE and its CEO, Vince McMahon.

Trump wrestles with "Stone Cold" Steve Austin at WrestleMania in 2007. Trump has close ties with the WWE and its CEO, Vince McMahon.

Trump attends the U.S. Open tennis tournament with his third wife, Melania Knauss-Trump, and their son, Barron, in 2006. Trump and Knauss married in 2005.

Trump attends the U.S. Open tennis tournament with his third wife, Melania Knauss-Trump, and their son, Barron, in 2006. Trump and Knauss married in 2005.

Trump attends a news conference in 2005 that announced the establishment of Trump University. From 2005 until it closed in 2010, Trump University had about 10,000 people sign up for a program that promised success in real estate. Three separate lawsuits -- two class-action suits filed in California and one filed by New York's attorney general -- argued that the program was mired in fraud and deception. Trump's camp rejected the suits' claims as "baseless." And Trump has charged that the New York case against him is politically motivated.

A 12-inch talking Trump doll is on display at a toy store in New York in September 2004.

A 12-inch talking Trump doll is on display at a toy store in New York in September 2004.

An advertisement for the television show "The Apprentice" hangs at Trump Tower in 2004. The show launched in January of that year. In January 2008, the show returned as "Celebrity Apprentice."

An advertisement for the television show "The Apprentice" hangs at Trump Tower in 2004. The show launched in January of that year. In January 2008, the show returned as "Celebrity Apprentice."

Trump dips his second wife, Marla Maples, after the couple married in a private ceremony in New York in December 1993. The couple divorced in 1999 and had one daughter together, Tiffany.

Trump dips his second wife, Marla Maples, after the couple married in a private ceremony in New York in December 1993. The couple divorced in 1999 and had one daughter together, Tiffany.

Trump and singer Michael Jackson pose for a photo before traveling to visit Ryan White, a young child with AIDS, in 1990.

Trump and singer Michael Jackson pose for a photo before traveling to visit Ryan White, a young child with AIDS, in 1990.

Trump signs his second book, "Trump: Surviving at the Top," in 1990. Trump has published at least 16 other books, including "The Art of the Deal" and "The America We Deserve."

Trump attends the opening of his new Atlantic City casino, the Taj Mahal, in 1989.

Trump attends the opening of his new Atlantic City casino, the Taj Mahal, in 1989.

Trump uses his personal helicopter to get around New York in 1987.

Trump uses his personal helicopter to get around New York in 1987.

Trump was married to Ivana Zelnicek Trump from 1977 to 1990, when they divorced. They had three children together: Donald Jr., Ivanka and Eric.

Trump was married to Ivana Zelnicek Trump from 1977 to 1990, when they divorced. They had three children together: Donald Jr., Ivanka and Eric.

Trump attends an event to mark the start of construction of the New York Convention Center in 1979.

Trump attends an event to mark the start of construction of the New York Convention Center in 1979.

Trump stands with Alfred Eisenpreis, New York's economic development administrator, in 1976 while they look at a sketch of a new 1,400-room renovation project of the Commodore Hotel. After graduating college in 1968, Trump worked with his father on developments in Queens and Brooklyn before purchasing or building multiple properties in New York and Atlantic City, New Jersey. Those properties included Trump Tower in New York and Trump Plaza and multiple casinos in Atlantic City.

Trump stands with Alfred Eisenpreis, New York's economic development administrator, in 1976 while they look at a sketch of a new 1,400-room renovation project of the Commodore Hotel. After graduating college in 1968, Trump worked with his father on developments in Queens and Brooklyn before purchasing or building multiple properties in New York and Atlantic City, New Jersey. Those properties included Trump Tower in New York and Trump Plaza and multiple casinos in Atlantic City.

Trump, center, wears a baseball uniform at the New York Military Academy in 1964. After he graduated from the boarding school, he went to college. He started at Fordham University before transferring and later graduating from the Wharton School, the University of Pennsylvania's business school.

Trump, center, wears a baseball uniform at the New York Military Academy in 1964. After he graduated from the boarding school, he went to college. He started at Fordham University before transferring and later graduating from the Wharton School, the University of Pennsylvania's business school.

Trump, center, stands at attention during his senior year at the New York Military Academy in 1964.

Trump, center, stands at attention during his senior year at the New York Military Academy in 1964.

Trump, left, in a family photo. He was the second-youngest of five children.

Trump, left, in a family photo. He was the second-youngest of five children.

Trump at age 4. He was born in 1946 to Fred and Mary Trump in New York City. His father was a real estate developer.

Trump at age 4. He was born in 1946 to Fred and Mary Trump in New York City. His father was a real estate developer.

President-elect Donald Trump has been in the spotlight for years. From developing real estate and producing and starring in TV shows, he became a celebrity long before winning the White House.

President-elect Donald Trump has been in the spotlight for years. From developing real estate and producing and starring in TV shows, he became a celebrity long before winning the White House.

Most striking has been Trump's aim at Muslims in the United States. He's been widely denounced for claiming that people in New Jersey — a state with "large Arab populations," he said — cheered after the terrorist attacks of September 11, 2001 . That, coupled with his seeming endorsement of a national registry to track Muslims in the country, has sparked a new level of condemnation from conservatives already on edge about Trump's endurance.

"Trump is a fascist. And that's not a term I use loosely or often. But he's earned it," tweeted Max Boot, a conservative fellow at the Council on Foreign Relations who is advising

Trump is a fascist. And that's not a term I use loosely or often. But he's earned it. https://t.co/KSfADd5Ycq — Max Boot (@MaxBoot) November 22, 2015

"Forced federal registration of US citizens, based on religious identity, is fascism. Period. Nothing else to call it," Jeb Bush national security adviser John Noonan wrote on Twitter.

Forced federal registration of US citizens, based on religious identity, is fasicm. Period. Nothing else to call it. https://t.co/XYee8dEgJr — John Noonan (@noonanjo) November 20, 2015

Conservative Iowa radio host Steve Deace, who has endorsed Ted Cruz , also used the "F" word last week: "If Obama proposed the same religion registry as Trump every conservative in the country would call it what it is -- creeping fascism."

If Obama proposed the same religion registry as Trump every conservative in the country would call it what it is -- creeping fascism. — Steve Deace (@SteveDeaceShow) November 20, 2015

Even one GOP presidential hopeful -- albeit a little-known candidate barely registering in the polls -- has used this language. In an interview with Newsmax TV on Friday, former Virginia Gov. Jim Gilmore said Trump's immigration policies, including the idea of creating a " deportation force " to remove undocumented immigrants from the country, amounted to "fascist talk."

The fresh accusations of fascist behavior are extraordinarily charged -- the term is often equated with Nazism. The use of such a loaded word marks one more step in the evolution of the establishment's view of Trump, from a political clown to something much more malevolent and dangerous.

Photos: Who's running for president? Photos: Who's running for president? Ted Cruz, Donald Trump, John Kasich, Hillary Clinton and Bernie Sanders, Hide Caption 1 of 6 Photos: Who's running for president?



"So, ladies and gentlemen, I am officially running for president of the United States, and we are going to make our country great again," Trump told the crowd at his announcement. Businessman Donald Trump announced June 16 at his Trump Tower in New York City that he is seeking the Republican presidential nomination. This ends more than two decades of flirting with the idea of running for the White House."So, ladies and gentlemen, I am officially running for president of the United States, and we are going to make our country great again," Trump told the crowd at his announcement. Hide Caption 2 of 6 Photos: Who's running for president?



"These are all of our stories," Cruz told the audience at Liberty University in Virginia. "These are who we are as Americans. And yet for so many Americans, the promise of America seems more and more distant." Sen. Ted Cruz of Texas has made a name for himself in the Senate, solidifying his brand as a conservative firebrand willing to take on the GOP's establishment. He announced he was seeking the Republican presidential nomination in a speech on March 23."These are all of our stories," Cruz told the audience at Liberty University in Virginia. "These are who we are as Americans. And yet for so many Americans, the promise of America seems more and more distant." Hide Caption 3 of 6 Photos: Who's running for president? Ohio Gov. John Kasich joined the Republican field July 21 as he formally announced his White House bid.



"I am here to ask you for your prayers, for your support ... because I have decided to run for president of the United States," Kasich told his kickoff rally at the Ohio State University. Hide Caption 4 of 6 Photos: Who's running for president?



"Everyday Americans need a champion, and I want to be that champion -- so you can do more than just get by -- you can get ahead. And stay ahead," she said in her announcement video. "Because when families are strong, America is strong. So I'm hitting the road to earn your vote, because it's your time. And I hope you'll join me on this journey." Hillary Clinton launched her presidential bid on April 12 through a video message on social media. The former first lady, senator and secretary of state is considered the front-runner among possible Democratic candidates."Everyday Americans need a champion, and I want to be that champion -- so you can do more than just get by -- you can get ahead. And stay ahead," she said in her announcement video. "Because when families are strong, America is strong. So I'm hitting the road to earn your vote, because it's your time. And I hope you'll join me on this journey." Hide Caption 5 of 6 Photos: Who's running for president?



"This great nation and its government belong to all of the people and not to a handful of billionaires, their super PACs and their lobbyists," Sanders said at a rally in Vermont on May 26. Sen. Bernie Sanders , an independent from Vermont who caucuses with Democrats, announced his run in an email to supporters on April 30. He has said the United States needs a "political revolution" of working-class Americans to take back control of the government from billionaires."This great nation and its government belong to all of the people and not to a handful of billionaires, their super PACs and their lobbyists," Sanders said at a rally in Vermont on May 26. Hide Caption 6 of 6

And it also reflects an increasingly visible and acute level of frustration and disbelief about Trump within the GOP, as Republicans view Trump's candidacy as an explosive mixture of economic populism with strongman personality politics. While it's unclear whether Trump is motivated by any coherent political philosophy, it's hard to recall another recent presidential candidate who has campaigned so openly on solving problems by sheer personal will.

The Trump campaign did not respond to a request for comment. Boot and Deace couldn't be reached for comment, and a Bush spokesperson did not respond to a request for comment on behalf of Noonan.

Academics who study fascism say that while Trump seems to have an authoritarian sensibility, his behavior doesn't meet the dictionary definition of fascism. The term describes an overtly anti-democratic movement that suppresses all opposition as a way to fulfill political goals, and a fascist leader is a dictator that wishes to exercise complete control, even by condoning violence.

Scholars of fascists like Benito Mussolini in Italy and Adolf Hitler in Germany (none of Trump's conservative critics have compared him to either man) say, however, that Trump does display some of the key characteristics of a fascist. His comments about a national registry for Muslim-Americans , together with his propensity to stir up anti-immigrant and xenophobic sentiments among his supporters, amount to a perception of hostility toward ethnic and religious minority groups.

"The most recent comment he said about creating a national registry of all Muslims -- that's very dangerous," said Steve Ross, a professor of history and scholar of fascism at the University of Southern California.

Ross, who proposes the label "right-wing bully" for Trump, said he can certainly understand why the question has come up. "You're talking about an American government that would move towards the persecution of citizens and people living within its own country," he said. "That is why people are saying, 'Gee, if you follow this through, it's fascism.' "

JUST WATCHED Trump would 'certainly implement' database for Muslims Replay More Videos ... MUST WATCH Trump would 'certainly implement' database for Muslims 00:45

"Fascism sometimes becomes an attribute to describe someone that is intolerant or totalitarian or even racist," said Federico Finchelstein, an expert on fascism at the New School who said Trump is better described a populist. "When dealing with an important part of the nation such as Hispanics, I think he definitely fits those categories."

When a reporter asked Trump last week how a national database of Muslims would be different from the persecution of Jews in Nazi Germany, Trump responded: "You tell me."

Historians say they see other characteristics of fascism in Trump in addition to his propensity for racial and ethnic stereotyping. Among them: nativist undertones, attempts to control the media; and even condoning violence against his critics.

At a Trump campaign rally in Birmingham, Alabama, a black protester was physically attacked by a handful of Trump fans in the crowd. Video captured by CNN shows the man being shoved to the ground, punched and at one point even kicked. The next day, Trump drew fierce backlash when he said that perhaps "he should have been roughed up."

The sentiment was then echoed by Trump's senior counsel Michael Cohen. "Every now and then an agitator deserves it," Cohen said on CNN's "New Day" Tuesday morning.

JUST WATCHED Trump: Maybe protester 'should have been roughed up' Replay More Videos ... MUST WATCH Trump: Maybe protester 'should have been roughed up' 00:59

Ross said the incident illustrates behavior that is only steps removed from fascism.

"We had the same thing happening in Germany in the 1920s with people being roughed up by the Brownshirts and they deserved it because they were Jews and Marxists and radicals and dissidents and gypsies — that was what Hitler was saying," Ross said. "I'm not saying Trump is Hitler, but the logic of condoning violence against those who oppose you -- you can imagine, a man who would condone it as a candidate -- what would he do as an official president?"

Trump's interactions with the media — in particular, his attempts to shut out reporters critical of his campaign —have also shown authoritarian tendencies.

The businessman regularly lashes out at reporters who give unfavorable coverage, and his campaign has denied credentials to journalists as retribution. Trump has more than once boycotted appearing on Fox News , in protest of what he has deemed unfair treatment.

JUST WATCHED Univision anchor: Journalists have to take a stand Replay More Videos ... MUST WATCH Univision anchor: Journalists have to take a stand 03:20

"What they expect from the media is praise. This is another element in this character and in other leaders of this type, which is that they are extremely messianic and narcissistic," said Finchelstein. "Whatever they see, they see as a personal attack against them."

History professor Robert Paxton of Columbia University, who has studied the rise and spread of fascism, said he would not call Trump a fascist. But Paxton also said he can understand why some people might be inclined to point out similarities between Trump and fascist leaders.

"He's good at making astonishing speeches that make people sit up and take notice. So there's some of that manipulation of public emotions that is visible with Trump," Paxton said. "Hitler and Mussolini -- no one had ever seen public rallies like the meetings they'd have. People were absolutely mesmerized."