--- - |2 What drives progressive public policy? Because progressive policy challenges the interests of powerful people and interests that dominate policy making, it is puzzling that progressive policy ever happens. This article addresses this question by modeling and appraising institutional political, political mediation, and policy feedback theories and models of progressive policy making. Institutional political theory focuses on political institutional conditions, bureaucratic development, election results, and public opinion. Political mediation theory holds that social movements can have influence over progressive policy under favorable political conditions. Policy feedback theory holds that programs will be self‐reinforcing under certain conditions. The article goes beyond previous research by including and analyzing public opinion in institutional political and political mediation models and addressing positive policy feedbacks. We appraise five models derived from these three theories through fuzzy set qualitative comparative analyses of the generosity of early old‐age policy across U.S. states at two key moments. We find some support for each theory, and the results suggest that they are complementary. Left regimes or social movements can initiate progressive policy, which can be reinforced for the long term through positive policy feedback mechanisms. We discuss the implications for current U.S. politics and for progressive policy elsewhere. - 'Sociological Forum, Volume 34, Issue 3, Page 553-571, September 2019. '