Drawing on a unique panel data set of supporters of the Alternative for Germany (AfD), the study shows that programmatic differences between supporters of Frauke Petry and Bernd Lucke cannot sufficiently explain the crucial intraparty leadership contest of July 2015. Programmatic differences were minor in 2013 but became pronounced over time. Politically active supporters were disaffected with the old moderate leadership of Bernd Lucke, who pursued an organizational reform to reduce the influence of the rank-and-file. Social media also played a key role for the leadership turnover, as alternative news sources on social media were only politicized by the intraparty opposition. It is conceivable that the structure of social media networks influences opinion formation processes and internal affairs of right-wing populist parties in general, as their supporters tend to have low trust in mainstream news.
