The state of positive modeling of constitutional choices is not much beyond where Buchanan and Tullock (1962) left it over twenty years ago. Since there has been substantial progress in the study of postconstitutional or ordinary policy decisionmaking, this paper reports an attempt to use these public choice ideas to shed light on the questions of constitutional choice. In particular, I try to see how outcomes in the constitutional arena may differ from those in the policy arena, and then use this insight to analyze the calling of constitutional conventions.