The videos that rolled across the television screen were startling: Americans beating each other with clubs and sticks on the streets of a quiet college town. White supremacists with torches; anti-fascists pushing back.

Kevin Boyle, an American history professor at Northwestern University, watched it unfold, the feeling in his gut both horror and a sense that the racial tension bubbling for years had finally, almost inevitably, begun boiling over.

“Given our political moment, I’m not surprised that we’ve come to this point,” he said. “I’m terribly depressed we’ve come to this point but I’m not surprised. It didn’t come out of nowhere.”

Historians and political scientists have been warning that American politics had become a pressure cooker, full of racial tension building once again to the point of a deadly clash, like the one in Charlottesville, Virginia, on Saturday that claimed three lives.

White supremacy has always lurked in America’s shadow, said Boyle, whose teaching focuses on the history of racial violence and civil rights. Then, he believes, President Trump was elected and emboldened their hate.

“Donald Trump gave them permission to come out into the real world,” he said.

On Saturday, more than 1,000 neo-Nazis, skinheads and Ku Klux Klan members descended on the city of Charlottesville to “take America back” by rallying against plans to remove a confederate statue. Hundreds came to protest against the racism, and the event spiraled out of control.

The violence had been building for months during a series of confrontations between members of the “alt-right” – a loose collection of white nationalists, racists and anti-immigration populists – and people who oppose them. It began the very day Trump put his hand on a Bible and took the oath of office. Skirmishes broke out at his inauguration between his supporters, some of them white nationalists, and those against him. More than 200 were arrested.

Richard Spencer, who is among the nation’s foremost white nationalists, and others of his ilk blame the other side. “With Trump’s election, the radical left of this country has come unhinged,” said Kyle Bristow, the founder of a law firm dedicated to alt-right legal advocacy.

But both sides agree on the general narrative of how the widening racial and ideological divide took root: Some white Americans began feeling left behind by progress. The decline of the white working class coincided with drastic cultural changes, like quickly diversifying demographics and the election of the nation’s first black president.

“With the election of Barack Obama, there was so much talk about being this post-racial moment, and on some levels it was extraordinary,” said Steven Hahn, a history professor at New York University. “But it didn’t take long for the really vicious racism to surface. It turned out to be an instigator of an enormous amount of rage, and I think Trump both fanned it and inherited it.”

Now white supremacist groups are actively trying to move into the mainstream. The Daily Stormer, a popular alt-right website, published a story in the run-up to the Charlottesville gathering, calling on followers to leave white hoods or Nazi costumes at home, and go for fitted shirts and suits instead, to attract recruits. They needed to look sexy, the author wrote.

Whether they might be successful in spreading their message depends a lot on how American leaders respond, said Boyle.

Trump quickly came under fire for his response. He said “we condemn in the strongest possible terms this egregious display of hatred, bigotry and violence on many sides, on many sides.”

The “on many sides” emphasized at the ending drew the ire of his critics, who pushed back on his statement as failing to specifically denounce racism and equating the white supremacists with those who came to protest their hate.

“The bottom line is if it weren’t for a bunch of neo-Nazis marching around it would have been a regular peaceful day in Charlottesville,” said Kyle Kondik, with the University of Virginia’s Center for Politics. “Whether he likes it or not, the president, the person that holds that office, is supposed to act as the person setting a moral standard for the country, and I think he’s been falling far short in that regard.”

He pointed to other Republican leaders who took a strong stand against the racists who descended on Charlottesville on Saturday.

Sen. Orrin Hatch, for example, tweeted: “We should call evil by its name. My brother didn’t give his life fighting Hitler for Nazi ideas to go unchallenged here at home.”

Kondik worries about how quickly the nation’s toxic political divides will continue seeping into all parts of American life if the president doesn’t realign the country’s moral compass.

“It’s been an ugly couple of days, and you just wonder if we’re backsliding in terms of race relations,” he said. “It’s an unpleasant thing to think about, but something we have to think about as a country.”