Studies on party membership have focused mainly on the profiles of members and on the reasons for joining (Seyd and Whiteley, 1992 and 2002; Scarrow, 1996; Heidar, 2006; van Haute, 2009a). Thus, party internal conflicts and discontent are hardly explained and very few studies have explored in depth party internal conflict (Boucek, 2009) or party internal discontent (van Haute, 2009b). This paper investigates one of the main dimensions of political discontent (Gamson, 1968): the specific support for the party, i.e. the satisfaction with its internal functioning. Taking the Belgian Socialist Party as a case-study, the paper analyzes this variable by looking at the attitudes towards intra-party democracy (Rüdig, 2005; Koole, 2009; Linek and Lyons; 2009; Wauters et al., 2009; Baras et al., 2010). These attitudes concern the perception of grassroots members of recent organizational changes such as the adoption of direct election of party leader or internal referendum (Scarrow, 1999; Allern and Pedersen, 2007; Seyd, 1999; Faucher-King, 2007). The paper explores the impact of members’ discontent on their political behavior (Campbell et al., 1964; Almond and Verba, 1965). Through the use of membership survey data (2010), the study takes into account the impact of discontent on intra-party mobilization and non-allegiant behavior (intent to leave, vote for another party and inclination to factionalism).