This article examines religious ideology construction, transformation, and decline across three protest campaigns (1867, 1886, 1890) of the "eight-hour" movement in nineteenth-century Chicago. I explore the ways four characteristics of movement ideologies (cultural resonance, contested discourse, frame correspondence, and instrumental credibility) are shaped by the internal dynamics of the movement and the changes in external circumstances that resulted from protest activity. Data are derived from Chicago's labor, religious, and secular presses, from pamphlets, and from speeches given by eight-hour proponents from three representative factions within the movement: the craft-based Chicago Trade and Labor Assembly, the Knights of Labor, and the radical Central Labor Union. Movement leaders transformed working-class religious culture into an ideological discourse because they believed religion could help them achieve concrete industrial reform. When religious ideologies did not resonate with intended audiences, build the movement's resource base, achieve political victories, or assist in building coalitions, they were discarded and replaced by other ideologies. This article contributes, then, to an understanding of the forces that both facilitate and constrain religion in collective action contexts.