This article pursues a developmental understanding of American parties as autonomous and thick collective actors through a comparison of four key historical actors we term “prophets of party”: partisans of the nineteenth-century Party Period; Progressive reformers; mid-twentieth century liberal Democrats; and activists in and around the body popularly known as the McGovern-Fraser Commission. Leading theories portray political parties as the vehicles either of ambitious politicians or of groups eager to extract benefits from the state. Yet such analyses leave underdetermined the path from such actors’ desires for power to the parties’ wielding of it. That path is mediated by partisan forms and practices that have varied widely across institutional and cultural context. As parties search for electoral majority, they do so in the long shadow of ideas and practices, layered and accreted across time, concerning the role of parties in political life. We analyze four such prophesies, trace their layered contributions to their successors, and reflect on their legacy for contemporary party politics.