Taking into consideration the limits of the Habermassian model of rational argumentation - highlighted by the Anglo-Saxon literature in particular -, this paper uses the critical discussion model elaborated by the pragmadialectical theory, to analyse the characteristics of on-line political discussions. Co-presence of multiple voices, organization of debates by participants themselves, and the absence of a settling of differences in viewpoints are explored through the excerpts of discussion forums on political issues in Qu?bec during the year 2005. On the basis of this analysis the author questions the rational dimension of political speech and reconsiders its agonistic counterpart.