Drawing on path-breaking work in which she and her colleagues isolated significant communication effects in the 2000 and 2008 presidential campaigns, the eminent political communication scholar Kathleen Hall Jamieson marshals the troll posts, unique polling data, analyses of how the press used the hacked content, and a synthesis of half a century of media effects research to argue that, although not certain, it is probable that the Russians helped elect the 45th president of the United States.