Zeynep Tufekci is a sociology professor at the University of North Carolina at Chapel Hill. She wrote “Twitter and Tear Gas: The Power and Fragility of Networked Protest.”

David Snyder is the executive director of the First Amendment Coalition. He comments on free speech issues.

Peter Simi is a sociology professor at Chapman University and has studied extremist groups and violence for more than two decades.

Arie Perliger is a security studies professor at University of Massachusetts Lowell. His research interests include political violence and extremism.

J.J. MacNab is a fellow with the Program on Extremism at George Washington University. MacNab is an expert on sovereign citizens, paramilitary militia groups and anti-government extremist organizations.

Gary LaFree is the founding director of the National Consortium for the Study of Terrorism and Responses to Terrorism at the University of Maryland. He created the Global Terrorism Database.

Seth Jones is a counterterrorism expert with the Center for Strategic and International Studies. Media contact is H. Andrew Schwartz.

John E. Finn is a professor emeritus of government at Wesleyan University in Middletown, Connecticut. He wrote “Fracturing the Founding: How the Alt-Right Corrupts the Constitution.”

Michael German is a fellow with the Brennan Center for Justice’s Liberty & National Security Program and a former FBI agent who infiltrated neo-Nazi terrorist groups as an undercover agent. Media contact is Mireya Navarro.