Comparative scholarship on health systems has largely relied on institutional approaches, based mainly on the public–private divide. This article argues that political dynamics are central to understanding the shaping and evolution of health systems. France offers a particularly instructive case due to the complexity of its system: intertwined public-private mix, changing modes of governance, persistence of historically rooted arrangements and institutional disjunctures. Drawing on policy tracing, with attention to critical realism, and conducting a contextual and historical analysis, the article shows how actor configurations, power resources, ideological conflicts and political crises have structured the French health system over time. The introduction presents the characteristics and paradoxes of the French system, which this article contributes to explain. The following two sections trace the separate institutionalisation of the two key policy actors: first, the nineteenth-century formation of the medical profession, structured as a national scientific elite, local political notability, and a corporatist organisation ; second, the belated and contingent construction of a national health insurance system, confronted with the resistance of organised medical liberalism. The third section analyses how the power relationship between the medical profession and the government have evolved after a major change of the political regime (Vth Republic) and pressure from economic and social challenges, such as modernizing hospital infrastructure, universalising access and containing expenditure. It shows growing government leadership, and yet limited statecraft over parts of health sector. The conclusion points to the interest of long-term policy tracing, as a method that allows to uncover underlying power structures and identify the causal factors of change, an approach applicable to other national cases.