This study uses case study research to examine the conditions of successful zoning policy changes meant to address housing affordability crises in Seattle and Minneapolis. Research revealed that existing political windows – due to the presence of progressive councilmembers and city staff – became the impetus for advocacy engagement. Grassroots activists then crafted framings tailored to their contexts to gain the support of environmental groups, city officials, and racial justice groups. A sense of conflict with Not-In-My-Backyard (NIMBY) opponents in turn mobilized coalition stakeholders to provide the political cover necessary for councilmembers to defend proposed changes. These findings provide a blueprint for affordable housing advocacy across the country, contributing to the cascade of campaigns that have emerged in recent years.