The phenomenon of banalisation, an advanced degree of institutionalisation of an instrument or of organisational practices, is frequently observed in the field of the social and solidarity economy (SSE), but is often analysed purely in terms of isomorphism. This article proposes a model for analysing the banalisation of an SSE instrument by examining the evolution of the institutional logics contributing to shaping it. It is based on a qualitative survey of the construction of the Pôle Territorial de Coopération Economique ("Territorial Clsuter for Economic Cooperation") policy. The analysis sheds light on the evolution of the institutional logics in play, in which the founding institutional logic of the instrument is effaced by a new institutional logic described as "imported." Based on a Gioia-type coding operation, an explanatory model of this evolutionary process is put forward, around two central dimensions: the incompatibility of the institutional logics present and the hegemony of reference to the market. The results contribute both to questioning the Public Value Approach and to enriching the corpus of the institutional logics approach by examining the institutional orders-institutional logics relationship.