Although research on effects of populist communication has increased, it is still unclear how populism in news articles affects the readers’ manifest behavior, such as whether and how they comment on online news. To address these issues, we conducted a content analysis of online news articles (N = 332) and corresponding reader comments (N = 2786) during election campaigns in France, Switzerland, and the United Kingdom. We find that populist key messages by political and media actors in news articles do not only provoke more reader comments but also prompt citizens to use populist key messages themselves in their comments – regardless of how journalists contextualize these statements.