Among the notable aspects of the Common Core State Standards (CCSS) is the diverse array of interest groups supporting them. These organizations must now apply the strategies they used so effectively in advancing the Common Core to stem mounting opposition to it. This article draws on theories of political and policy learning and interviews with major participants to examine the role that CCSS supporters have played in developing and implementing the standards, supporters' reasons for mobilizing, and the counterarguments and strategies of recently emerging opposition groups.