This chapter shows that the decline in challenger quality could be explained by rising campaign costs. To conduct a more rigorous test of the impact of the two state-level institutional features on challenger quality, the author incorporate them as additional explanatory variables in the individual-level analysis, focusing in on the years 1974 to 2012, for which these key variables were available. The results of these empirical analyses suggest the decline in competitiveness is the most reliable explanation for the decline in challenger quality observes between 1972 and 2018. The results of the analyses suggest that higher challenger spending in an election exerts a positive effect on the probability of an experienced challenger in the subsequent cycle. The interactive model describes the relationship as a conditional relationship, meaning the effects of each of the key independent variables on the dependent variable vary according to the level of the other independent variable.