Cyberwar examines the ways in which Russian interventions not only affected the behaviors of key players but altered the 2016 presidential campaign’s media and social media landscape. After laying out a theory of influence that explains how Russian activities could have produced effects, Jamieson documents the hackers and trolls’ influence on the topics in the news, the questions in the presidential debates, and the social media stream. Drawing on her analysis of messages crafted and amplified by Russian operatives, changes that Russian-hacked content elicited in news and the debates, the scholarly work of other researchers, and Annenberg surveys, she concludes that it is plausible to believe that Russian machinations helped elect Donald J. Trump the 45 th president of the United States.