This article analyzes the often fraught yet sometimes productive relationship between the modern presidency and social movements. Although the presidency–social movement nexus is fraught with tension, collaboration between the White House and social activists was indispensable to the important changes that occurred during the second half of the twentieth century. Focusing especially on Lyndon Johnson's uneasy but critical relationship to the civil rights movement and Ronald Reagan's enlistment of the Christian Right into the Republican Party, we trace the emergence of a novel form of politics since the 1960s that joins executive prerogative, grassroots insurgency, and party polarization. Johnson's efforts to leverage presidential power to advance civil rights played a critical role in recasting the relationship between national administration and social movements, one that paved the way for a national conservative offensive. The relationship forged between Johnson and the civil rights movement has echoes in the similar joining of the Reagan presidency and the Christian Right, an executive-insurgency alliance that instigated the transformation of the Republican Party and spurred the development a new presidency-centered party system by the end of the 1980s.