Partisan and apportionment bias in creating a predominant party system

Moving beyond the analytical characteristics of apportionment methods or election systems, this article focuses on their outcomes in practice. We illustrate how apportionment and partisan biases working with a high threshold created an electoral environment conducive to the establishment of a predominant party system. We use the historical example of the Turkish experience. We trace the historical development of disproportionality for the entire multi-party elections for the 1950–2015 period. Focusing on the five most recent elections of this period since 2002, we demonstrate how the biases introduced by the apportionment method in use and the 10% threshold have advantaged the leading Justice and Development Party (Adalet ve Kalkınma Partisi, AKP). Our study suggests that a partisan bias favoring AKP still continues to exist at a lower level even after correcting the apportionment and the threshold biases. We underline how these biases form the foundation for a conservative over-representation and emphasize the path-dependent dynamics that keep challengers to the AKP away from the electoral scene, effectively helping to continue its hegemonic position in the system.