This article proposes an endogenous perspective on policy change, combining the analysis of the policy process (policy framing, decision and implementation) with the analysis of the transformation of professional groups and their organizational representation. It deals with the case of territorial undersupply in primary care provision, which has become a key issue in healthcare policies in France and Germany since 2000 (the analysis goes up to 2018). Policy changes in these two health insurances systems cannot be explained only by the salience of the problem, framed as “medical deserts” in France and as “lack of physicians” in Germany. We propose an explanation based on the internal fragmentation of the medical profession, playing a paradoxical role: as limiters of change (for the established and institutionalized organizations) and as promoters of change (for the medical entrepreneurs shaping new organizations defining and supporting new primary care service structures).