This article investigates the extent to which populist key messages are distributed via online news articles and reader comments, as well as how media actors, political actors, and readers employ populist online communication during election periods. Populism is defined as a thin ideology, and four dimensions of populist communication are distinguished: people-centrism, anti-elitism, popular sovereignty, and exclusion. We analyze online news articles and reader comments during election campaigns in France, the United Kingdom, and Switzerland. We find that comment sections are more populist than online news articles and that the majority of populist key messages in online news articles originate from politicians, not from journalists. However, we further show that compared with straight news items, opinion-oriented stories are more prone to conveying populist key messages from media actors, whereas straight news favors populism by political actors. Finally, we investigate how online news media moderate populist key messages disseminated by political actors.