This analysis examines the influence of state, district, and candidate-level factors on the reelection prospects of state legislative incumbents. Campaigns in 14 states over two election cycles (1996 and 1998) are used to determine how various conditions result in the likelihood that incumbents are challenged, the strength of the challenge they face, and the percentage of the vote they receive in contested elections. A major concern is determining the influence of policy responsiveness of incumbents relative to institutional characteristics (e.g., legislative professionalism) and district-level conditions (e.g., past winning-vote percentage). What role does each set of factors play and at what point in the election process are their effects realized? Findings show that institutional and district factors are strong determinants of both the likelihood of a challenge as well as the strength of a challenge. Policy responsiveness of incumbents has a small influence, mostly on voter support. Overall, the findings provide insight into the factors responsible for incumbent success and electoral competition in state legislative elections.