The idea of an all-encompassing partnership has vindicated all sorts of collaboration models to be articulated as partnerships although not occurring as ones, leaving practitioners and politicians of regional development planning with suboptimal ways of collaborating. Reviewing the partnership literature depicts similar difficulties in delineating partnerships from other collaboration models causing diversified messages about partnerships. In an attempt to invigorate the partnership literature by delineating partnerships from other forms of collaboration and thus progress the work and output of regional planning and development, this paper defines a partnership to be a promise of a promise denoting other collaborative models such as network, cluster and governance-partnership as a promise only. Based on qualitative interviews, discursive analyses and strategic documents, the comparative case analysis of two Danish regional development agencies shows how one remained as a governance-partnership while the other turned into a partnership by continuously creating possibilities for the groups of actors involved. This transformation from a promise only into a promise of a promise displays how to delineate partnerships from other forms of collaboration such as networks, clusters and governance-partnerships.