ABSTRACT This paper describes public reason communitarianism, a theory which is isomorphic to public reason liberalism. It contains the same internal diversity and debates, and the same fundamental structure and argumentation as public reason liberalism. However, while public reason liberals believe that public reason will converge on liberal outcomes, hypothetical public reason communitarians hold that public reason converges, for largely the same reason, on communitarianism. From the outside, there seems to be no good grounds for preferring one over the other. We offer this theory as a challenge for public reason liberalism, as it poses a dilemma. If public reason liberals admit the coherence of the communitarian version of their view, then public reason does not uniquely generate liberal outcomes, and indeed in the real world probably fails to justify liberalism, even to all reasonable people committed to public reason. If liberals want to deny the coherence of the view, though, it seems they must rely on question-begging liberal premises or question-begging interpretations of key concepts in the public reason view. Thus, contrary to their self-understanding, their view is ideological after all.