What explains the passage of Thailand's landmark universal healthcare (UHC) policy? In separate contributions, Selway and Harris emphasized the role of electoral rules and political parties, on one hand, and “professional movements” of developmentally minded state bureaucrats on the other. Which is correct? In this article, Selway and Harris respond to each other's work. While Selway agrees that the actions of the professional movement constitute an underappreciated necessary condition for universal healthcare in Thailand, he argues that Harris overstates the role of the movement in implementation. Harris defends his position and maintains that an institution-focused account is insufficient, arguing that the actions of Thailand's Rural Doctors’ Movement not only explain universal healthcare but also gave rise to the very electoral rule changes that Selway argues were so critical to facilitating universal coverage. Selway responds to these criticisms, and the two researchers jointly consider implications for causation, qualitative research, and policymaking theory.