Matthew Heimbach, at center in red hat, clashed with a protester at a rally for Republican presidential candidate Donald Trump in Louisville, the day after Trump’s Super Tuesday victories. (Reuters)

“Get out! Leftist scum! Get out!”

In the video, the bearded white man wears a black shirt and a red baseball cap with the words “Make America Great Again.” He is yelling at a young black woman. He shoves her once, then again, screaming at her to leave. The crowd around him is agitated. Others push the woman as well. Many are yelling.

There had been ­clashes between supporters and protesters at Donald Trump rallies before, but this one in Louisville last month stood out. The racial imagery was jarring, the violence only barely contained. When video of the encounter went viral, most who saw it had no idea who the man was. But his followers knew. And so did his family. And so did the people who track hate groups and white-supremacist ­organizations, who consider him one of the country’s leading young proponents of racial acrimony.

The day after the rally, Matthew Heim­bach, a 25-year-old white nationalist who grew up in an affluent Maryland community and now lives in rural Indiana, acknowledged online that he was the one in the video pushing the woman. The object of his fury, Kashiya Nwan­guma, 21, a public health major at the University of Louisville, has joined two others in suing Trump in Jefferson County Circuit Court for allegedly inciting a riot. The suit also ­accuses Heim­bach of assaulting Nwan­­guma.

In his post online, Heim­bach described her as a member of the Black Lives Matter movement who had been disrupting the event for the better part of an hour. “White Americans are getting fed up and they’re learning that they must either push back or be pushed down,” he wrote.

In an interview, Nwan­guma said she is not affiliated with any organization and attended the rally to peacefully protest Trump’s policies.

“It’s hard for me to think about that day,” she said. And it’s hard for her to forget Heim­bach. What stays with her, Nwan­guma said, is “the blind rage and hatefulness and aggression” that she was met with as she was being shoved.

“It was a new side of humanity that I hadn’t quite seen before,” she said. “I know it looks like I’m smiling, but I was really in disbelief. I was like: ‘What is going on and why is this happening? There’s no way that people are acting like this.’ ”

Heimbach’s supporters cheered his actions, praising him for standing up to the protesters. But for those who have been tracking his rise, the video raised new worries about Heim­bach. Some compare him to David Duke, a former Ku Klux Klan grand wizard and the country’s best-known white nationalist.

“I think Heim­bach should be taken as seriously as David Duke,” said Ryan Lenz, the editor of the Southern Poverty Law Center’s Hate­watch blog. He describes Heim­bach as a media-savvy millennial who has forged relationships with Storm­­front, the League of the South, the Aryan Terror Brigade, the National Socialist Movement and other white-supremacist organizations.

“He’s the affable, youthful face of hate in America,” Lenz said, “and in many ways, he’s the grand connector between all of these groups.”

David Duke has a long history in politics and the white supremacy movement. Here are key moments in Duke’s life in the public eye. (Claritza Jimenez/The Washington Post)

Heimbach doesn’t hide his extremism. He has had his picture taken at the U.S. Holocaust Memorial Museum in Washington holding a sign that said: “6 million? More like 271,301.” In another photo, in front of the Rev. Martin Luther King Jr.’s grave site in Atlanta, he unfurled the first flag of the Confederacy. After terrorist attacks in Brussels last month, he tweeted, “Hey Brussels, how’s that multi­culturalism working out for you?”

His racial worldview has cost him jobs and led to his excommunication from his Orthodox Christian church. It has created a rift between him and his parents and confounded those who knew him in Maryland: his classmates at Poolesville High School and his teachers and many fellow students at Montgomery College and Towson University, from which he graduated with a history degree in 2013.

Why, they ask, would someone as smart and educated as Heim­bach choose to assert that the Holocaust never happened, that lynchings in the South were mostly deserved, that apartheid in South Africa was not as bad as people have suggested and that if white Americans don’t set off a homeland for themselves, then the future of white America is in jeopardy?

‘We’re under attack’

On a weekday afternoon, members of Heim­bach’s Traditionalist Worker Party are gathered in the back of a tattoo parlor tucked behind a tanning salon and an auto detailer in Madison­ville, Ky.

Heimbach has driven three hours to this western Kentucky coal region from his home in Paoli, Ind., a quaint town of 3,600 founded in the early 1800s by Quakers seeking to establish a slave-free territory. There he works as a landscaper and lives with his wife, Brooke, and their 8-month-old son, Nicholas, who is named for the last czar of Russia.

Heimbach, wearing a black T-shirt with the words “Refugees NOT Welcome,” meets with Colton Williams, 23, a dishwasher, and Chappy, 37, a tattoo artist who didn’t want to use his full name because he has received threats for his involvement in pro-white activities. In Madisonville and neighboring small towns struggling with high unemployment rates, the three men and other party members have been going door to door distributing literature and encouraging people to join their movement supporting “faith, family and folk.”

“We don’t consider ourselves a hate group at all,” Chappy said. “We don’t hate anybody.”

Heimbach concurred. “We advocate for our people, but I don’t wish pain or death or suffering for anyone else.”

What they want, they say, is to make sure that elected officials are addressing the needs of poor and blue-collar whites. They want to run candidates in local elections. They want to siphon votes from mainstream Republicans. They want an end to illegal immigration; an end to outsourcing; an end to same-sex marriage; an end to abortion; an end to foreign aid, except disaster relief; and an end to attacks on European American identity. That’s the short-term plan.

The long-term plan is grander. Heim­bach foresees the United States being divided into autonomous racial states, with white Christians free to live apart and outside the control of any federal authority. Other racial groups would have their own lands, and an area would be set aside for people who wanted to continue living in a multi­cultural society. The goal would be for each race to protect its identity, and for Heim­bach, that means protecting whites.

“The system, which is a multi­ethnic empire, doesn’t care about us,” he said. “We’re under attack. White people need an advocate.”

‘Infected with this hatred’

Marilyn Mayo has been tracking Heim­bach’s doings for five years. A director of the Anti-Defamation League’s Center on Extremism, Mayo keeps a watchful eye on individuals and organizations that support racist and anti-Semitic ideologies. Heim­bach elicits more worry than most, she says.

“We’ve been concerned about him because he goes beyond just talking,” she said. “He’s created groups. He’s building ties. He’s obviously someone who can write about topics intellectually, and he’s college-educated. But he also wants to have very strong ties with hard­-core groups like neo-Nazis and racist skin­heads.”

Heimbach insists that his movement doesn’t promote violence. For him, inclusion on lists of avowed racists and extremists is more a badge of honor than a sign that he has crossed any line.

His party is still nascent. There are maybe a few hundred followers and a dozen or so chapters nationwide. But it will grow, Heim­bach says, because whites are being ignored in favor of minorities. And no one has pointed that out more clearly to the rest of the nation, he says, than Trump, who has emerged as the front-runner for the Republican presidential nomination, in part by promising to bar Muslims from entering the country and to build a wall to keep Mexicans out.

“Hopefully this [election] will really damage the Republican Party as a whole and awaken white working-class and middle-class people that the Republicans don’t represent them,” Heim­bach said. “So I really like Trump for that. But he’s not one of us. He’s not a white nationalist.”

Whether Trump becomes president doesn’t matter. Either way, Heim­bach predicts, his movement will win.

“Our movement is on the rise,” he told a gathering of the Council of Conservative Citizens in St. Louis last month. “And Donald Trump is just the first glimmer of the dawn that is about to rise. What he has shown us is that our people will not go quietly into the night. They want to fight.”

Heimbach sees a model for what his political party can accomplish in Europe, where far-right parties have gained strength in recent years in response to economic uncertainty, terrorist attacks and the migrant crisis. He has traveled to Greece to meet with leaders of that country’s fascist Golden Dawn party, and in Germany he addressed the National Democratic Party, the country’s ultra­nationalist political party. Britain has banned him from traveling there.

Last summer, Heim­bach spoke in California at Camp Comradery, a gathering of far-right nationalists, skinheads and white supremacists.

“The next time we have this conference, I want to see twice the amount of people here,” he said. “In 10 years, I want a Nuremberg rally.”

‘He’s wasted his life’

“Self-radicalized.”

That’s how Heim­bach describes his racial awakening. Growing up in Poolesville, a once-rural, increasingly diverse Montgomery County community with a median household income of $150,000 a year, Heim­bach had no personal encounters that led to his racist ideology. It certainly wasn’t something he learned from his parents: Karl and Margaret Heim­bach, schoolteachers who divorced when he was in his early teens.

“His family does not share his beliefs in terms of race or religion,” Margaret Heim­bach said in a brief telephone interview. His father declined to comment.

The gen­esis of Heim­bach’s worldview came from two books he read in high school: “Who Are We? The Challenges to America’s National Identity,” by Samuel P. Huntington, and Patrick J. Buchanan’s “The Death of the West.” And everything else, he says, he discovered online.

At Poolesville High, Heimbach tried to start a white student union after a similar group was formed for African American students. He says more than 100 students signed his petition. Deena Levine, the school’s principal, declined to discuss Heim­bach.

But Christine Simmons, a former classmate who is white, says he made other students feel very uncomfortable.

“He wouldn’t use the n-word or any slurs, but he would say this is a white community and those people don’t belong here,” Simmons said. “He was always very rude to anyone who wasn’t like him or didn’t think like him.”

At Montgomery College, Heim­bach went out of his way to be offensive in a number of Joe Thompson’s history classes, his former teacher says. He once wore a shirt that said “All I need to know about Islam I learned on 9/11,” and on his laptop he displayed a bumper sticker with a Confederate flag and the words “If I had known all the trouble they would cause, I would have picked the cotton myself.”

Thompson says that Heim­bach was smart but sifted history to fit his needs. “When he debates history, he leaves out those inconvenient facts that hurt his argument.” What Thompson also thought he saw in Heim­bach was someone who was looking for a father figure.

“It makes me sad. It seems to me like he’s wasted his life,” Thompson said. “I did see some goodness in him. But I also did see that he was infected with this hatred.”

Heimbach acknowledges that some of his tactics at Montgomery College were over the top. He says, for instance, that his understanding of Islam and respect for the religion have grown. But he has always employed attention-grabbing stunts.

In 2012, as a student at Towson University, north of Baltimore, he founded a white student union to “celebrate European heritage.” The university refused to sanction the group, but Heim­bach and his small band of followers weren’t deterred. They would later post on their website that they were there to protect white students from “black predators” and that “White Southern men have long been called to defend their communities when law enforcement and the State seem unwilling to protect our people.”

He knows that provocation generates publicity and that publicity works, even if it comes with costs.

“I guarantee you that I’m going to recruit members out of this article, no matter how badly you slant it,” he said. “Thousands of people will look us up online, and maybe a dozen will join the party.”

But the costs do cut. His father has not met Heim­bach’s son, and Heim­bach can’t foresee a way for them to reconcile. His brother and sister haven’t spoken to him in years, he says. Last year, the Orthodox Christian church Heimbach joined in Indiana shunned him for his beliefs.

His work life, too, has been affected. Earlier this year, Heim­bach was training to be a family case manager for the Indiana Department of Child Services until, he says, his bosses­ learned about his views. The department said in a statement that Heim­bach was dismissed because his “behavior in training was disruptive of the workplace and incompatible with public service.”

Heimbach says he hasn’t ignored the rebukes or the calls for him to rethink his beliefs. He simply doesn’t agree with them. It is everyone else who needs to open their eyes.

“They don’t realize how bad the problems are,” he said. “They don’t realize what’s out there. You can’t just wait out the storm and hope everything is going to be okay.”

Jennifer Jenkins contributed to this report.