This article aims to identify the representations and social imaginaries, as socio cognitive and significant systems, that were staged in the advertising spots of the Rejection and Approval coalitions in the 2020 plebiscite campaign in Chile; and present a methodological tool, the semiotic analysis of discourse, which, starting from the minimum unit of analysis of the sign and five procedural stages, from the denotative to the connotative level, jointly evidences these representations and imaginary. All of this is supported by three theoretical pillars, political communication, political discourse and the difference between representations and social imaginaries. The social representations that were identified at the denotative level of the Reject Option are linked to the family; power as public order; private property and patriotism. In the Approve Option, social mobilization, communitarianism and police repression. The four social imaginaries that emanated from the connotative level were: Otherness, Axiological, Sameness and Temporal.