Portland, Oregon (CNN) In this stereotyped mecca of liberal idealism lies a deep-seated subculture that just recently shocked the country: the white supremacist movement in Portland.

Not long ago, that phrase might have seemed oxymoronic. But a recent triple stabbing has cast a spotlight on the city's tensions between the alt-right and the alt-left.

"Portland has a long history of a battle between the right and the left," said Randy Blazak, a professor of criminology at the University of Oregon.

It's a long-simmering conflict that heated up after President Donald Trump's election. And experts say Portland -- like other liberal hotbeds -- could see more conflict in the months to come.

'You call it terrorism, I call it patriotism'

The most recent feud played out both inside and outside a hearing for slaying suspect Jeremy Joseph Christian

Christian is accused of fatally stabbing two men who tried to protect two African-American girls, including one wearing a hijab, on a Portland light-rail train.

"Go home, we need American here!" Christian shouted at the girls, according to a probable cause affidavit. "I don't care if you are ISIS."

On Tuesday, Christian had barely entered the courtroom when he started shouting in his blue jail uniform.

"Free speech or die, Portland!" Christian bellowed. "... Death to the enemies of America. ... You call it terrorism, I call it patriotism. You hear me? Die."

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Just outside the courtroom, vitriol flew from the other direction.

One man identified himself as a friend of Christian's and was instantly met with profanity from some supporters of the victims.

"F*cking Nazi, you're a fascist!" one person shouted at the man.

"I bled for my race," he replied, as he tightened the red shoelaces on his boots.

Red shoelaces have historically been used by racist skinheads "to identify themselves as white power skinheads," the Anti-Defamation League said.

It's not clear what the man meant when he said he bled for his race. Sheriff's deputies escorted him out before any more trouble erupted.

It's far from the first time Portland has been linked to Nazi extremism.

Flashback to 1988 murder

At the Portland metro station where bloody victims emerged last week, mourners wrote messages in chalk to honor those killed.

One message stirred memories of another gruesome murder: "Remember Mulugeta Seraw."

A message in front of Portland's Hollywood metro station honors murder victim Mulugeta Seraw.

"The murder of Mulugeta Seraw really put Portland on the map for all the wrong reasons," said Blazak, who is also chairman of the Oregon Coalition Against Hate Crimes.

Seraw, an Ethiopian immigrant, was bludgeoned to death with a baseball bat by a group of Portland skinheads in 1988.

"This city had a wake-up call," Blazak said. "It was kind of a sleepy, progressive city where we recycled everything. And then all of a sudden we had these roving gangs with Nazi skinheads attacking -- and in this case killing -- an immigrant."

'Skinhead City'

Skinheads had been known to recruit from the heavily white states of Oregon, Washington and Idaho -- part of a "Northwest Imperative," The Oregonian reported.

And in the years following Seraw's death, Portland gained the unsavory nickname of "Skinhead City."

"We became famous in the 1990s as 'Skinhead City' because of the rival gangs of right-wing racist skinheads and anti-racist skinheads who are doing physical battle in the streets," Blazak said.

Last week's deadly train incident "is kind of the latest manifestation of that," he said.

Protests on the rise since the election

In recent years, Portland has enjoyed a reputation as a friendly, peace-loving, quirky city -- an image further fueled by its portrayal in the IFC comedy " Portlandia ."

But conflicts have escalated in recent months, Portland Police Chief Mike Marshman said.

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"With the election of President Trump, I think our protest activity -- the number of events we have -- has increased," he said.

"That's problematic for me only because that takes more money to have those events go safely. I have to pull officers and detectives from their normal day-to-day activity, so certain crimes just now aren't getting investigated, or the investigations that are being worked on just take longer to work through the investigative process."

In the two days after Trump's inauguration, protesters caused about $1 million in damage, Marshman said.

Blazak, the Oregon criminology professor, said Portlanders are known to be passionate about politics.

"There is kind of a radical history in this town and in this region on both sides of the political spectrum," he said.

So who are the alt-right and alt-left?

The terms are relatively new, but the concepts are not.

For years, the alt-right has existed in the cyberworld, "but now they're kind of spilling over into the streets," Blazek said.

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"They're disaffected with mainstream conservative speech, (but) they don't want to be associated with overt white supremacist neo-Nazi groups, and they want to express anti-immigration views, anti-multicultural views, economic protectionism."

He said alt-right protesters are typically "moderate-income working-class white males who are left out of the globalization and ... feel left out of all the progress that's happening," the professor said.

"And they want to assert their voice because they feel like the tendency is to defer to the minority voice, and they feel like they're not part of the conversation."

By contrast, the alt-left -- also known as the Antifa -- is bent on stopping the rise of right-wing groups.

"The Antifa isn't a group, it's an idea. It stands for 'antifascist,' " said Ryan Lenz of the Southern Poverty Law Center . "They frequently engage in violence to make their point."

He cited a 2012 case in which alt-left activists "walked into a high-end restaurant in Chicago where a white supremacist group was eating and literally beat them up with baseball bats."

Blazak said the recent train killings, combined with political rhetoric, portends "a long, hot summer in Portland as these groups kind of line up against each other."

What's next for 'bastions of liberalism'

It might seem self-defeating for right-wing activists, and especially alt-right activists, to try to make headway in traditionally liberal hot spots like Portland and Berkeley, California.

Recent planned visits by Milo Yiannopoulos and Ann Coulter to the University of California, Berkeley, were met with protests, including some that turned violent

Blazak said he's not surprised alt-right members are trying to raise their profiles in such cities.

"There's this mantle of free speech that they're hanging their hats on," he said.

"Under the first amendment, they have a right to express themselves ... but it's used in a very provocative way to bring out the opposition and essentially martyr themselves in these street battles between the left and the right and to show themselves as almost the victims of the oppressive left-wing regime."

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But Joey Gibson, organizer of the group Patriot Prayer USA, said his group's planned rally in Portland on Sunday is "really not about provoking, it's about fighting for your right to assembly and to show what you believe in."

Gibson said he's libertarian and not alt-right. He said one of his goals is to help "turn a blue state into a red state."

That could be a huge challenge.

"Portland is as left as you can get," said Lenz of the Southern Poverty Law Center.

He said what's happening with the alt-right in Portland is actually reflective of what's happening across the country.

"What the alt-right is trying to do is they are going into these bastions of liberalism and hoping and willing to engage in physical conflict with counterprotesters," he said.

"The story isn't an Oregon thing. It's a national story."