Is there—or could there be—a Europe-wide public sphere? Some argue that one already exists, others that none is attainable. This debate turns on what it means to have one—on how much (and what kinds of) cross-border ‘discussion’ and public input it must entail. An ambitious European public sphere would involve more truly Europe-wide collective will formation and political accountability. This article attempts to move beyond speculation, with a discussion on an ambitious version of a European public sphere. Participants' opinions and vote intentions in Europolis were gauged before and after deliberating. This enables us to probe a double counterfactual: what if there was a more ambitious European public sphere, and what if European Parliamentary elections were consequently more deliberative.