The health of any democratic system depends on political ambition to generate a steady supply of quality candidates for office. Because most models of candidate entry assume ambition rather than model it, previous research fails to understand its roots in individual and institutional characteristics. We develop a two-stage model of progressive behavior that distinguishes between the formation of ambition for higher office and the decision to enter a particular race. Using data from a survey of state legislators, we demonstrate that the intrinsic costs and benefits associated with running for and holding higher office shape ambitions but do not influence the decision to run. For progressively ambitious legislators, the second-stage decision is a strategic choice about
whento run rather than whetherto run. Our research highlights how institutional characteristics that foster progressive ambition also increase the likelihood that national or local political conditions will be translated into meaningful choices at the ballot box.