Environmental activists are increasingly resorting to private strategies such as boycotts and protests focused on changing individual firms’ behavior. In this paper, we examine activists’ use of such “private politics” to engender firm compliance with activist objectives. We begin by developing a simple theoretical model of an activist campaign from which we develop a set of empirical hypotheses based on a set of observable features of firms. We test our hypotheses using a unique dataset of environmental activist campaigns against firms in the United States from 1988 to 2003. This paper fills an important need in the literature as one of the first empirical attempts to examine the private political strategies of activists and has important implications for the burgeoning literatures on industry self-regulation and the nonmarket strategies of firms.