Although the concept of “charismatic” leaders is commonplace in political discourse, many academics hold that the notion is vague and these leaders’ alleged appeal to voters untestable. This chapter sets out a conceptualization of such leaders, focusing on radical mission, personal presence, symbiotic hierarchy, and Manichean demonization. It then considers four broad theories about why charismatic leaders have notable effects (and why the radical right gathers support): socioeconomic change and crisis, political opportunity structures, cultural legitimation, and psychological affinities. While it is important not to overstate the powers of most leaders, the chapter concludes by arguing that we need to appreciate the role of “coterie” charisma over an inner core, helping to keep parties together. Moreover, charismatic leaders exert a centripetal appeal, particularly to authoritarians and/or those least interested in politics, creating a more differentiated following than the affective bond stressed in the classic Weberian model.