White nationalist extremism is an increasingly dangerous global security threat. However, how white nationalist leaders deploy their ideological rhetoric online to maintain and expand their base of support is not well understood. Using a novel dataset of 16,627,018 Twitter and Gab posts from 2016-2021 by 64 U.S. white nationalist leaders and 11,303 follower accounts, we examine leaders' promulgation of white nationalist ideology on social media and its effects on follower rhetoric and engagement. We find that when leaders highlight specific issues, their followers become significantly more likely to post similar content over the next several days. Moreover, gendered rhetoric by white nationalist leaders is a powerful `gateway appeal,' even more-so than partisanship, attracting primarily peripheral followers and leading users to subsequently post more racialized content themselves. These results provide insight into how white nationalist leaders market their extremist ideology, with important implications for understanding and disrupting patterns of online radicalization.