‘Only unity saves the Serbs’ is the famous call for unity in the Serb nationalist doctrine, but even though this doctrine enjoyed widespread ideological adherence, disunity has been a dominant characteristic of Bosnian Serb politics since the first multiparty elections in 1990. In this context of intra-Serb rivalry, the dominance of the Serb Democratic Party (Sprska demokratska stranka, SDS) has nevertheless been an almost constant feature. The SDS was founded in July 1990, under the leadership of Radovan Karadžić, and in a nationalist landslide in the elections four months later, the party secured around 85% of the Serb vote. Following the marginalisation of the competing non-ethnic parties the SDS enjoyed a largely monolithic status in the Serb community, but after the outbreak of war, and an initial closing of ranks, Serb opposition parties soon emerged. Such competition intensified after the signing of the Dayton Agreement, when the SDS's ability to use repressive powers against competitors was significantly reduced. Despite this persistent competition, the SDS has remained the dominant political force among the Serbs in Bosnia and until 1997 its control was close to being absolute. This dominance was decisive for the development of conflict and war in Bosnia, but analysis of the conditions that allowed the SDS to achieve and maintain its dominance is nevertheless lacking. In this article, the dynamics of intra-Serb party competition in Bosnia will be analysed and the following questions will be sought answered: What was the basis of the SDS's continued dominance? What resources were decisive in the party competition? How did the ethnification of politics affect these dynamics? How did the existence of intra-ethnic challengers affect the SDS's position?