Party system institutionalization and the durability of competitive authoritarian regimes

Party system institutionalization (PSI) is regarded as a critical underpinning of democracies, but its role in non-democratic systems has been understudied. In this paper, we evaluate whether the concept has meaningful and perhaps unique implications for the durability of competitive authoritarian regimes. We argue that a modified version of electoral volatility – the most common measure of PSI in democracies – conveys useful information about PSI in competitive authoritarian contexts by signalling the ability of the ruling party to manage the opposition. To this end, we construct an original data set that disaggregates electoral volatility into ruling party seat change and opposition party seat volatility and further divides opposition party volatility into Type-A and Type-B volatility. We find robust results that democratization becomes more likely when decreases in the ruling party's seat share coincide with an increase in opposition party Type-B volatility. This paper demonstrates that the concept of PSI has utility for understanding regime dynamics in competitive authoritarian contexts.