This chapter argues that we can observe social, political, and institutional developments that have contributed to variation in the p, B, and C terms, and that these changes can help to explain the decline in challenger quality between 1972 and 2000. It examines the impact of each of these state-level, structural, or institutional factors on challenger quality in congressional elections. Few developments with respect to the politics of congressional elections over the past three decades have been as pronounced as the changes in the costs of a campaign. Scholars have also examined the impact of a variety of structural and institutional factors measured at the state level that appear to be related to challenger quality. The chapter develops a variety of empirical models to predict the emergence of an experienced challenger in contested elections for the US House.