Political doctrines rarely show up in a pure form, but they rather come up mixed with other doctrines, with which they have relationships (more or less wide) of hybridisation. The aim of the essay is showing an exemplary case of these processes of hybridisation through the analysis of Madame de Staël and Constant's work between 1795 and 1803. The republican discourse developed within them, in order to answer to the circumstances' challenge, becomes contaminated with principles, practices and institutions belonging to the traditions of Liberalism, Political Realism and Anglo-American Constitutionalism. The most complete attempt to ideological and institutional modernisation of Republicanism can be traced back in Madame de Staël, to whom we owe the first formulation of 'Modern Liberty', as well as the claim of an experimental conception of Constitutionalism (that looks up to the best English and American practices). Constant' s thought is closer to the classical Republican tradition, but during the last years of the century opens up to Anglo-Saxon constitutional suggestions, through the theory of neutral power. [ABSTRACT FROM AUTHOR]