Current theories of community-based collaborative governance arrangements rely on the presence (or absence) of certain antecedent community conditions as well as incentives for institutional change deriving from the sociopolitical and economic environment. The combination of antecedent conditions and incentives is helpful in understanding why collaboratives emerge and succeed in “easy” cases (strong incentives, conducive antecedent conditions). Yet the combination is of little help in understanding the institutional change puzzle for collaboratives in “tough” cases (strong incentives, poor antecedent conditions). Examination of a “tough” case in the Blackfoot watershed (Montana), which eventually blossomed into a successful collaborative, shows the importance of a particular set of new ideas, or shared norms, around which participants coalesced. These new ideas for understanding public problems, the community itself, and the relationships among stakeholders, became a broad conceptual framework for guiding stakeholder interaction as they attempted to manage the many public problems facing the watershed.