This study offers an empirical description of the voting alignments that dominated the American Constitutional Convention as the delegates struggled to produce the final report of that historic assembly. Its conceptual roots are firmly planted in the theoretical traditions of Schattschneider on conflict and cleavage, and of Key, Burnham and Sundquist on critical realignment of the American party system. I demonstrate that dynamic processes analogous to Key's conception of “critical elections” at the macro-level of national politics can also be identified and analyzed at the micro-level of the constituent assembly. Therefore, I argue that one of the “mainsprings of American politics,” as Burnham calls the critical election phenomenon, permeates all levels of the American political system and not simply the national level of electoral mass politics. More specifically, this clear description of coalition alignment, operation and realignment in the Constitutional Convention, when informed and enlightened by the “critical realignment” model, greatly facilitates the more traditional discussion of debate, conflict and ultimate decision on the central issues before that body—representation, federalism, senatorial authority, and the nature of the executive in a republican government.