This study examines how the structure of intraparty power shapes the motivations of individuals who join political parties and remain party members. I also examine how the organizational structure affects the types of activities that party members engage in. Drawing on organizational statutes for over 20 parties in six countries, I first develop vertical and horizontal indicators of intraparty power. I then test how these dimensions affect member recruitment, retention, and activity with individual level data from the European Social Survey. The results indicate that the internal structure of power within political parties has important implications for party organizations and their mobilization capacity as well as the functioning of modern democracy more broadly.
