Following the victory of the Constitutional Revolution, the National Consultative Assembly (Majlis) was institutionalized as the central legal and political authority of the new order. However, political developments prevented constitutionalists from achieving their intended goals. The end of the World War I renewed efforts to restore parliamentary governance. However, the final outcome of this period was the decline of the parliamentary system in Iran.This article examines why attempts to revive parliamentary governance in the early 1300s (1920s) ultimately failed. It argues that the period between the end of World War I and the change of dynasty represented a critical juncture in Iran’s political history. During such moments of uncertainty, political institutions are shaped less by formal legal continuity than by struggles among competing centers of power. In this context, the success of any political project depended on the ability of political actors to correctly identify the fundamental crisis facing society and to offer practical solutions for transforming existing conditions.Using the analytical framework of historical institutionalism, with a focus on critical junctures, the study shows that the postwar period was a time of profound redefinition of Iran’s political structure. Political institutions were reshaped through conflicts among rival actors and ideas. The findings indicate that supporters of the parliamentary system failed to accurately diagnose the core crisis of Iranian society and were unable to present an effective and workable response. Consequently, they were gradually marginalized, and the parliamentary ideal they promoted failed to achieve practical realization within the emerging political order.