The long war over party structure in American politics, rooted in the 1820s and joined in the 1880s, was still alive and well when postwar political science returned to its fortunes in the 1960s. Yet an array of systematic indicators of these fortunes, beginning in the 1950s and running through the 2010s, suggests that this war did indeed have a major turning point around 1970. Impelled afresh by a lesser but parallel conflict over the proper institutional forms for presidential selection, the old model of organized parties, built around a hierarchy of long-serving party officeholders, was decisively defeated by a newer model of volunteer parties, built instead around participatory networks of issue activists. That much of the existing study of this long war was mainly just confirmed by systematic contemporary measures.