This paper discusses the role of the electoral system in making the Justice and Development Party (AKP) dominant. Drawing on Sartori's framework, we first clarify the concept of a predominant party system. Second, we examine the impact of the electoral system on the emergence of a predominant party system in Turkey. Analysing election results, we argue that the electoral system fosters dominance in three ways. First, a combination of electoral formula, national threshold and district threshold leads to over-representation of large parties and under-representation of small ones. Second, the fear of a wasted vote due to the high threshold prompts voters to support their second-best option, which concentrates the votes among large parties. Finally, the electoral system increases electoral turnout rates by extending polarization.