The deadly synagogue shootingin Pittsburgh, the killing oftwo African-Americans in Kentucky and the wave of improvised explosive devices aimed at critics of President Trump all happened just within the last week.
And they all coincide with deep national pessimism about the outlook for peaceful politics in the United States.
Last year, after a shooter opened fire on Republican lawmakers at a baseball practice outside Washington, D.C., a CBS News poll found that 73 percent of Americans felt the tone of the political debate encourages violence.
Since then the concept of a new civil war has seeped out into the open, especially on the right.
"The Civil War on America's Horizon," reads a headline in last month's The American Conservative. On Townhall.com, a Trump supporter imagined how a civil war would turn out, in an article entitled "Why Democrats Would Lose the Second Civil War, Too."
Meanwhile, The Federalist ran an op-ed advocating the breakup of the United States, arguing that it "may seem a bit outlandish now, but you won't think so once real domestic unrest comes to your town."
The extreme fringe has also picked up on the notion.
Here's how one anonymous person framed a threat to The New York Times' Ken Vogel on his voicemail, earlier this year. Vogel postedthe recording on Twitter.
"You are the enemy of the people. And although the pen might be mightier than the sword, the pen is not mightier than the AK-47," the caller said. "And just remember Ken, there's nothing civil about civil war."
Carolyn Lukensmeyer is the head of the National Institute for Civil Discourse at the University of Arizona. The organization was formed after a shooting injured then-Arizona Democratic Rep. Gabby Giffords in 2011. The incident also killed six and wounded twelve others aside from Giffords.
"I have to say that I've been surprised at the number of times where we're holding a discussion ... across differences and someone will actually say that they believe we could come to a civil war again in the United States," she told NPR.
But then, she said, many people back off from their initial conclusions: "They do say, 'No, I don't really believe that we'll have a civil war, but I find some of what I see happening frightening enough to think of it that way.'"
Experts who study violent conflict in foreign nations say they are now seeing worrying similarities here at home.
"I already think we've seen some pretty dangerous signs, the most important of which is the demonization of opponents," said Sheri Berman, a professor of political science at Barnard College, Columbia University.
"The second step is seeing people as unable to be dealt with or compromised with, and that can fairly easily slip into more extreme kinds of behavior," she said.
Mike Jobbins works for Search for Common Ground, a nonprofit that tries to reduce political violence abroad in places like Burundi, Congo and Yemen.
He told NPR that violence breaks out when people no longer feel like they can work with others in a different societal group.
"Prior to some of these conflicts that erupted you see a drop in the capacity to deal with one another, and to focus on one sort of prevailing identity," he said. "That's something we see here in the U.S. as we look at some of the partisan political divisions."
Polarization — and political violence — is far from unprecedented in America. Between January 1969 and April 1970, the United States experienced 4,330 bombings, according to The New York Times.
"I came of age during the Vietnam War, so I came of age in a time in which differences on policy issues did lead to violent civil protest, that did lead to blood in the streets, so do I think it is possible? It's part of my own life experience," said Lukensmeyer.
The way to prevent disagreements from becoming violence, according to experts in civil conflict, is to be more open to those with whom you disagree.
"The biggest challenge that many people have in their own lives is really in taking the first step to — when you disagree with someone, to listen first," Jobbins said. "I think as you look at the U.S. today, we are entering a period of conflict ... but even if conflict is inevitable, violence is not."
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