Most of the researches on modality has been concerned with what modality does in terms of qualifying the proposition. Over the last decade, other perspectives have become prominent within the field. It is now generally accepted that modality as stancetaking has, in addition to its qualificational function, well recognized interactional, textual and rhetorical functions, such as persuading, manipulating, challenging, confronting, accepting, encouraging the flow of discussion, creating cohesive texts. As Aristotle noted in his Rhetoric, ordinary argumentation deals with “things that could be otherwise”. It is obvious therefore that argumentation is seen as deeply intertwined with modality, the semantic category corresponding to the human ability of relating to non actual states of affairs; and that modality has been an important concern of modern argumentation theory. In this article we try to argue that modality plays an essential role to the establishment of argumentative discourse relations between utterances in political discourse.