The social and solidarity-based economy (SSE) plays a pivotal role in the territorial processing of public problems, as evidenced by the French Territorial Groupings of Economic Cooperation (TGEC). Far from limiting itself to an addition of corporate legal statuses, the SSE aims here at nurturing the very models of territorial developments. Significantly, the South Aquitaine TGEC, based in Tarnos (Landes) aggregates around twenty SSE bodies, public authorities and for-profit companies within one project of territorial cooperation. Constituting a TGEC consists in a discrete and contained construction and processing of territorial public problems. Nevertheless, public problems are subject to constant political work on the part of stakeholders. This political work aims first at bringing together initially distinct sector-based public problems (youth employment, social and economic development, equilibrium between productive and residential economy, gender equality, creation of economic activity, territorial short circuits, small farming, food) in order to merge them into a shared territorial project. The political work then aims at harmonizing distinct social constructions of public problems, varying according to the territories engaged in the cooperation. These public problems can aggregate on a virtuous manner, but they can also be subject to potential tensions when prioritization is needed.