The American Federation of Labor and Congress of Industrial Organizations (AFL-CIO) was connected to the cause out of a desire to motivate college students to become involved in its labor-organizing campaign. Other allied labor unions (here, academic labor unions) were also potentially connected to this goal. In 1996, the AFL-CIO developed the Union Summer program--a 6- to 10-week summer internship for college students. It taught students about global labor injustice and labor organizing each summer until 2001 (Featherstone & United Students Against Sweatshops, 2002). This analysis draws on national data sets and publicly available information about campuses and union activities to present a model of an external organization's influence in campus organizing. The purpose of this study is to begin to understand the extent to which campuses are vulnerable to--or at risk of--outside influences from other social movement actors. Research questions include, What campus characteristics increase the chances that its students: (1) will be targeted by an external organization for participation in the cause; and (2) will seek out an external organization to advance a cause? Also, (3) what types of campuses are most vulnerable to, or at risk of, the direct influence of external organizations' efforts to engage students in a cause? By considering the factors that predict recruitment to the AFL-CIO's Union Summer program, student participation in the program, or both, it is possible to understand the conditions that expose campuses' students to the influence--or perhaps at times, intrusion--of political and ideologically linked external organizations.