This article analyses the genesis of expertise in public opinion polls in Argentina in the 1980’€™s and the social and political conditions of the success of the instrument. Its institutionalization is related to the transformations of forms of political perception and action and to the success of the future pollsters, who offered the polls as a cognitive and symbolic tool to actors in the political and journalistic fields when the process of the so-called democratic transition began. The objective is to show, firstly, in what way political changes affecting Argentina since 1983 (end of a military dictatorship, defeat of Peronism) are conditions of possibility for the institutionalization of polls as political tools. Secondly, how the expert-pollsters contributed to the “modernization”€ of the political field. Finally, how, in order to impose the legitimacy of their instrument, they have constituted a specific space at the border of the political, media and university fields.