The purpose of this paper is to determine whether the discursive units of the prototypical conversational discourse can be applied to the characterization of the interactions that occur daily on Twitter. This has been tested on a corpus of 500 tweets, sent by the most active Spanish deputies and senators on this network, while they “talk” to citizens. First, we describe the conditions or factors that affect the external variation of discourse in this context; second, we explore the realizations, that is, the linguistic mechanisms adopted by speakers within the level of enunciation. To this end we address, first, the study of monologic units such as intervention and act; then we focus on those of exchange and dialogue, which rely in part on interactive markers.