His main focus is on the role of the political information environment in structuring attitudes, with a special interest in the proliferation of digital media. He has also written extensively on affective polarization, or the increasing hostility between Democrats and Republicans. Before joining the University of Pennsylvania, he was faculty at the Amsterdam School of Communication Research. He received his Ph.D. from Stanford University. His research has appeared or is forthcoming in various journals across disciplines, including the American Journal of Political Science, PNAS, the Journal of Politics, the Annual Review of Political Science, and the Journal of Personality and Social Psychology, and has been covered in many news outlets, such as the New York Times, the Washington Post, and the Atlantic.