Comparative-historical research on medicalization is rare and, perhaps for that reason, largely ignores political institutions, which tend to vary more across countries than within them. This article proposes a political-institutional theory of medicalization in which health care policy legacies, political decentralization, and constitutionalism shape the preferences, discourses, strategies, and influence of actors that seek or resist medicalization. The theory helps explain why abortion has been more medicalized in Britain than the United States. The analysis finds that the American medical profession, unlike its British counterpart, focused on defending private medicine rather than protecting its power to "diagnose" the medical necessity of abortions; that American political decentralization aided the establishment of abortion on request by encouraging strategic innovation and learning that shaped social movement strategies, medical issue avoidance, and the growth of nonhospital clinics; and finally, that constitutionalism promoted rights discourses that partially crowded out medical ones.
Keywords: abortion; medical profession; medicalization; political institutions; social movements.