Thinkers committed to an ideal of public reason are suspicious of religiously informed political activity as it undermines democratic political legitimacy. This paper considers Jürgen Habermas’s recent shifts on this question in light of the history of Europe’s religious parties in the late 19th and early 20th centuries. These parties made a real and lasting contribution to Europe’s democratization and their history suggests ways in which Habermas and other defenders of public reason misunderstand the nature of democratic political legitimacy.