Drawing upon mainly qualitative inquiry with political, associative and economic actors over a two-decade long period, the article seeks to provide answers to a key conundrum that challenges, in different ways, territorial politics scholars, as well as those working primarily on France. What are the conditions for a successful form of regional advocacy in a unitary state? The French region of Brittany has a specific mode of operation, one based on mixing identity and instrumental claims, and accessing a repertoire of responses that are not naturally open to other French regions. A related question follows logically from the first: Can a specific territorial model developed in one set of conditions adapt when circumstances change? The Breton case demonstrates limited evidence of endogenous change (a central tenet of discursive institutionalism), though it does admit a continuing capacity to filter external pressures in a way that makes sense to regional actors. Analytically, the article develops territorial political capacity as a part material, part constructed framework that can be used for comparing regions at a particular point in time, as well as for capturing the evolution over time of a specific region.