America has a problem with political violence—and it’s growing.

The recent rise in political violence in the United States is troubling but not surprising to researchers who study the topic. “We know the factors that put countries at risk for political violence,” he said. Barbara F. Walter, an expert on violent extremism. “We also know the factors that put countries at risk for election violence, and the United States has all of those factors.”

Walter, a professor at the University of California, San Diego and author of How the Civil War Started, among many other books, spoke to me in this week’s episode Inside the hive that she is worried about the upcoming election—but doesn’t think the threats will subside after that. “We’re going to have a tough few months,” Walter said. “I think, actually, we’re going to have a tough 10 years.”

That’s because the underlying risk factors are clear. “The countries that tend to experience violence around elections are those that have winner-take-all elections, as the United States has; they have voters and populations that have become deeply divided,

especially by race, religion, and/or ethnicity; they have weak institutions, or they have democracies that are not as strong as they should be and where some voters question the validity of elections; and they have a candidate who has lost in the past,” Walter explains. “These are conditions that social scientists have found by looking across countries and over time.” And all of those conditions exist in the United States today.

Donald Trump, “It’s making his supporters believe that if he loses again, it’s stolen from them,” she added. “So again, it’s a perfect recipe for violence. We’re going to have violence around this election. And really, the bottom line is, are we prepared for that?” Thinking ahead and preparing for the possibilities, she said, “is much better than burying your head in the sand and pretending that everything is fine.”

Regarding the recent threats on Trump’s life, Walter said that “the two big drivers of the rise in assassination attempts are guns, and especially the easy access to assault weapons,” and the internet as a source of radicalization. People are “surfing the internet and they’re in these chat rooms and they’re getting radicalized,” she said. “They’re starting to believe the conspiracy theories that they’re hearing. And a lot of them are mentally unstable to begin with.”

On the subject of civil war, Walter notes that “there is a cancer growing in the United States” because a segment of the population no longer believes that democracy serves them. She says the two best predictors of civil war are “whether a country is a partial democracy,” as opposed to a vibrant democracy or an oppressive autocracy, and “whether its citizens are divided, deeply divided along racial, religious, or ethnic lines.”

When you have a democracy in decline, that’s when you start to run into trouble, Walter said. She asserted that political science data suggests that the United States has fallen into this “middle ground” in recent years. “Most of the violence happens in the middle ground.” The key is preparation: “We need to pay attention. We need to take precautions. We need to be prepared.”