Preaching democracy: The second Vatican council and the third wave

•We use variation in religious doctrine produced by the unexpected Second Vatican Council to investigate the impact of religion on democratization.•We adopt a difference-in-difference approach to estimate the council's impact on democracy.•We provide historical narratives on how the post-conciliar Catholic church influenced the democratization process in different national contexts.•Our research substantiates that the church played a decisive role in third wave democratization.