Some conservatives have seized on Wednesday's shooting of Republican Rep. Steve Scalise and three others as the latest example of what they see as rising political violence from the left. Fox News' Sean Hannity accused Democrats of "dehumanizing" Republicans, and the right-leaning Washington Times ran an editorial by a Tea Party activist that called leftist protests "the first skirmishes of the second American civil war."
But those who track extremism say that while there are a few far-left groups that raise red flags, their numbers remain small.
Much of the conservatives' anger has been aimed at "Antifa" — short for "anti-fascists." Antifa are loosely affiliated groups of mostly young people, mainly on the West Coast but spreading around the country.
They dress in black and wear masks when they confront right-wing groups; in the past few months there have been clashes or confrontations in Berkeley, Calif.; Portland, Ore.; and, just this week, on the campus of Evergreen State College, in Olympia, Wash.
"The moment we got here, they started throwing rocks," says Joe Allen, one of the right-wing protesters who descended on the college Thursday to challenge what they see as its leftist ideology. They were met by a large number of the masked, black-clad counterprotesters. Allen says the Antifa have been harassing Trump supporters since Election Day.
"That night we went to downtown Portland to see what everything was like, and we got stuck on the bridge because [the Antifa were] stopping all traffic, hitting cars, jumping on cars, asking people, 'Who did you vote for?' "
A heavy presence of police in riot gear kept the confrontation at Evergreen State from escalating. The leader of the conservative protesters and the "Patriot Prayer" movement, Joey Gibson, was slightly injured — he said someone threw a can at his head. He later found his tires slashed. Witnesses say masked counterprotesters did it.
Antifa rarely talk to reporters and rarely give their names, at least not while wearing masks. But in online discussions they say the far-right activists are being disingenuous. They point to what they regard as the racism and white supremacist ideology of the other side. They say groups such as Gibson's only pretend to be interested in peaceful political protest and would attack minorities or leftists, given the chance.
"People are desperate," says one masked counterprotester, a student at Evergreen State who gave his name as Felix. "They see the government turning back to regressive Reaganomics and racist undertones and rhetoric, so once they start kicking 25 million people off health care, then you're going to start seeing riots."
The idea that some on the far left are openly condoning violence is a red flag for extremist group monitors.
"This is a dangerous game; people are going to die. No one's died yet, but it's just a matter of time," says J.J. McNabb, an expert on political extremism at George Washington University.
McNabb says white supremacists and neo-Nazis are widely condemned — and deservedly — for their violent tendencies. But she says the Antifa shouldn't get a pass on their violence just because they oppose white supremacists.
"These guys are odious, [but] attack them with words. Don't come in with sticks and nails in them," she says.
Antifa are not new. They're a latter-day version of the anarchists and "black bloc" groups who, over the years, have often challenged police and broken windows during May Day protests in Seattle and Portland. Their membership is hard to track, but it appears to be expanding beyond the West Coast. They are also embracing other leftist causes beyond just fighting white supremacists.
Still, their numbers are tiny in relation to the mainstream political left. And, say experts, it's misleading for right-wing groups to suggest that the Antifa are more violent than right-wing extremists.
"The far left is very active in the United States, but it hasn't been particularly violent for some time," says Mark Pitcavage, a senior research fellow at the Anti-Defamation League's Center on Extremism.
He says the numbers between the groups don't compare.
"In the past 10 years when you look at murders committed by domestic extremists in the United States of all types, right-wing extremists are responsible for about 74 percent of those murders," Pitcavage says.
You have to go back to the 1970s to find the last big cycle of far-left extremism in the U.S. Both Pitcavage and McNabb say we have been in a predominantly far-right extremist cycle since the 1990s — the abortion clinic bombings and Oklahoma City, for example. And, more recently, racially motivated attacks such as the one at a Sikh temple in Wisconsin, the mass shooting at a black church in Charleston, S.C., and last month's stabbings on a commuter train in Portland.
Still, Pitcavage says Wednesday's shooting attack on Republican members of Congress is a warning sign. He is especially concerned because the shooter apparently was not particularly extreme in his political ideas; his views were seemingly in the mainstream left.
"One act does not a trend make," Pitcavage wrote after the shooting attack. "But I am concerned that, in this highly polarized and divided society, more people who have stances that fall within the mainstream, on the left and right alike, may consider political violence an attractive option."
Domestic terrorism experts say that concern is only heightened by the fact that the line between what's considered mainstream and what's considered fringe is becoming increasingly blurred.
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Far-right pundits are seizing on this week's shooting at a congressional baseball practice as an example of what they say is a rise in the left-wing violence in the U.S. Experts who monitor domestic terrorism had been warning about the potential for left-wing radicalization as a backlash to President Donald Trump. But as NPR's Kirk Siegler reports, they're hesitant to call it a trend at this point.
KIRK SIEGLER, BYLINE: Lately here on the West Coast we keep seeing theatrical street confrontations between far right and far left - Berkeley, Portland, and just last night on the campus of The Evergreen State College in Olympia, Wash.
UNIDENTIFIED MAN #1: Move it. Move it.
SIEGLER: It takes dozens of police in riot gear to keep these two groups apart. The right-wing group came to protest what they see as campus' overly liberal ideology. Their leader is a guy named Joey Gibson. And just a few minutes in he's nursing a bleeding eyebrow.
JOEY GIBSON: You know what you get in these hardcore liberal areas? They threw a can, hit me right in the face.
SIEGLER: Gibson is talking about a large group of leftist protesters often called antifas, short for anti-fascists. They wear black and hide their faces. And they never give their names, especially when my colleague, Martin Kaste, asks why they're carrying sticks.
MARTIN KASTE, BYLINE: Can I ask what the sticks are for?
UNIDENTIFIED MAN #2 AND UNIDENTIFIED WOMAN #1: No.
KASTE: I can't ask what the sticks are for.
UNIDENTIFIED WOMAN #1: No.
UNIDENTIFIED MAN #2: I mean, you can, but I'm not going to tell you.
SIEGLER: The antifas say they're here to counter what they see as the right's violence and creeping fascism. This masked student gives his name as Felix. He says given the current political situation violence is to be expected.
FELIX: You know, people are desperate, and they see the government turning back into the aggressive Reaganomics and racist undertones and rhetoric. So once they start kicking, like, you know, 25 million people off the health care then you're going to start seeing riots.
SIEGLER: The idea that some on the far left are openly condoning violence is a red flag for extremist group monitors like J.J. MacNab. She says the clashes between antifas and far-right protesters on the West Coast are increasingly volatile.
J J MACNAB: This is a dangerous game. People are going to die. No one's died yet, but it's just a matter of time.
SIEGLER: Antifa's membership appears to be growing beyond its traditional West Coast base while also embracing other leftist ideas beyond just fighting white supremacists. MacNab says white supremacists are widely condemned - and deservedly - for their violent tendencies. But she worries antifa is getting a pass with violence just because they're attacking racists.
MACNAB: Attack them with words. Don't come in with sticks with nails in them.
SIEGLER: On the far right, activists are trying to exploit the idea that groups on the far left like antifa are the ones inciting the violence.
(SOUNDBITE OF ARCHIVED RECORDING)
UNIDENTIFIED WOMAN #2: They use their schools to teach children that their president is another Hitler.
SIEGLER: This online video was produced by the National Rifle Association.
(SOUNDBITE OF ARCHIVED RECORDING)
UNIDENTIFIED WOMAN #2: To smash windows, burn cars, shut down interstates and airports, bully and terrorize the law-abiding.
SIEGLER: The actual data tell a much different story. Mark Pitcavage tracks domestic extremism for the Anti-Defamation League.
MARK PITCAVAGE: The far left is very active in the United States, but it hasn't been particularly violent for some time.
SIEGLER: According to the league's data, in the past 10 years 2 percent of all murders associated with extremist ideology came from the left. Seventy-four percent came from the extreme right, including the mass shooting at a black church in South Carolina, last month's deadly stabbings on a Portland commuter train. Pitcavage says you have to go back to the 1970s to see a real cycle of deadly violence from the left.
PITCAVAGE: But because of the controversial nature of the Trump presidency and some of the things that have occurred over the past six months there legitimately is a chance that we could see more violence from the left. And, you know, that should concern everybody.
SIEGLER: Domestic terrorism experts say that concern is only heightened by the fact that in the current polarized country what's considered mainstream and what's considered fringe is getting more blurry. Kirk Siegler, NPR News. Transcript provided by NPR, Copyright NPR.