["Environmental Policy and Governance, Volume 36, Issue 2, Page 253-262, April 2026. ", "\nABSTRACT\nThe governance of shared water systems requires collaboration across diverse stakeholders. In this study we advance the theoretical understanding of asymmetric collective action problems (CAPs) by reassessing the role of third‐party interventions and emphasizing the strategic importance of policy brokers and institutional venues. Drawing on insights from the Advocacy Coalition Framework (ACF), we argue that policy brokers can play a pivotal role in bridging divides, fostering dialogue, and enabling “small‐scale” solutions within complex governance settings. Empirically, we examine a case from Sweden's largest water system, where municipalities with asymmetric upstream–downstream positions negotiated the creation of a Water Protection Area. The study is based on interviews with local decision‐makers. We illustrate how structural asymmetries in power, influence, and risk exposure, in combination with heterogeneous local interests, shape both incentives and capacities for cooperation. Our findings suggest that the presence—or even the perceived potential—of third‐party involvement may foster a more conducive environment for coordination. We conclude by underscoring the strategic role of policy brokers in mediating between actor coalitions and the significance of institutional venues as platforms for consensus‐building.\n"]