Part for the literature views high numbers of presidential candidates as a threat to political stability in presidential democracies (Jones 2004, Golder 2006). A contradictory model proposes that an overconcentration of the presidential party system is problematic (McClintock 2013). Both models are hard to reconcile. We approach this puzzle by arguing that the relationship of the level of fragmentation to governability crises is curvilinear: both the very low and very high effective numbers of presidential candidates increase the risk of governability crisis. We test these theoretical claims through ordered logit model drawing on a sample of 113 presidencies in Latin America between 1978 and 2013 using an ordinal index of the intensity of crisis as the dependent variable. We explore the operation of the theorized causal mechanisms through case studies and formulate implications for the design of presidential electoral rules drawing on the debate contrasting runoff and plurality rules.
