Concerns range from isolated violent incidents to a long stretch of mass protests, violent confrontations between extremists and widespread property damage, if the outcome of the election remains unclear or is hotly contested for weeks or months, according to security consultants, analysts of extremism, police officials and local elected leaders who spoke with CNN.

“It keeps me up at night,” Cincinnati Mayor John Cranley, who chairs the US Conference of Mayors’ Mayors and Police Chiefs Task Force, about the threat of violence. “I’m also worried that there will be a bogus attempt to prevent the counting of all the ballots, and that also could lead to a variety of unrest in a variety of ways.”