Mainstreaming as a meta-process: A systematic review and conceptual model of factors contributing to the mainstreaming of radical and extremist positions

Abstract Over the past decade, extremists have increasingly aimed to integrate their ideologies into the center of society by changing the presentation of their narratives to appeal to a larger audience. This process is termed (strategic) mainstreaming. Although this phenomenon is not new, the factors that contribute to the mainstreaming of radical and extremist ideas have not been systematically summarized. To identify elements fostering mainstreaming dynamics, we conducted a systematic literature review of N = 143 studies. The results demonstrate that mainstreaming’s gradual and long-term nature makes it particularly difficult to operationalize, which is why it often remains a buzzword. In this article, we propose a novel conceptualization of mainstreaming, understanding it as two communicative steps (content positioning and susceptibility), and present 12 contributing factors. These factors can serve as starting points for future studies, helping to operationalize mainstreaming, empirically monitor it, and, subsequently, tackle its (long-term) effects.