This study investigates divergent patterns of political discussion in 28 online forums initiated by the European Commission as part of the 2009 European Citizens' Consultations. Despite having identical technological and process designs and connections to the policy process, the forums displayed significant differences in discussion intensity. A hypothetico-deductive approach tested three hypotheses about favorable conditions for political discussion, finding that discussions were more intense in forums with lower levels of consensus among participants. A comparative case study of two forums revealed that organized groups' efforts to mobilize support for their positions contributed to high consensus levels. The findings highlight the importance of considering participants' strategies and behaviors to understand online political discussions.