Institutional Constraints on Social Movement “Frame Extension”: Shifts in the Legislative Agenda of the American Federation of Labor, 1881–1955

"Frame extension" is an important frame-alignment strategy for increasing social movement membership. Little research has addressed how the institutional environment of a social movement organization constrains and compels the organization to extend its frame among potential adherents. Elaborating on the bargaining perspective and the concept of multiorganizational field, we develop market and political models of the impact of social movement dependence relations with movement antagonists and political opportunity on frame extension. Our examination of these models with a multivariate time-series regression analysis of changes in the legislative agenda of the American Federation of Labor (AFL) over its complete history suggests that the AFL extended its frame among potential adherents in response to declining employer dependence on unions for labor-supply and increasing political opportunity. We conclude with implications of the findings for future research on contemporary union decline and institutional and environmental influences on social movement frame-alignment processes.