This article examines the historical significance of Barack Obama's creation of “OFA,” a presidential grassroots organization. It attempts, as Theda Skocpol has put it, to analyze American political development “as it happens.” Born as “Obama for America” during the 2008 campaign, OFA was renamed “Organizing for America” and ensconced in the Democratic National Committee during Obama's first term, where it served as the “grassroots arm” of the party. After 2012, it was spun off as a nonprofit social-welfare entity called “Organizing for Action” dedicated to advocating for Obama's second-term objectives: immigration reform, efforts to fight climate change, gun safety legislation, LGBT rights, and the implementation of health reform in the face of continuing intense opposition. That OFA was kept intact after Obama's successful election and reelection efforts marks it as an especially pioneering effort. Making use of several personal interviews, a wealth of primary documents, and data on spending and mobilization tactics, we explain how Obama's paradigm-shifting organization marked an effort to meet the challenges of forging a new progressive coalition in a fractious polity. More broadly, the article considers how this digital age grassroots effort has been influenced by, and in turn has contributed to the advance of an executive-centered partisanship characterized by high expectations for presidential leadership in a context of widespread dissatisfaction with government, strong and intensifying political polarization, and high-stakes battles over the basic direction of domestic and foreign policy programs.