After the events of Khordad 15, 1963, the institution of religion and clergy, which had always been the most important historical obstacle to republicanism in Iran, adopted a neutral stance against the dualism of “the divine right of the Shah” and “the secularity of the republic.” From that time until the 1978 revolution, three major movements sought to establish a republican government: Islamist movements led by Taleghani, Bazargan, Shariati, and Bani Sadr; the People’s Mojahedin Organization with Hanif Nejad’s ideas; and the People’s Devotion guerrillas with theorists such as Bijan Jazni and Masoud Ahmadzadeh. This research, relying on the theoretical framework of “liberation theology” and the descriptive-analytical method, attempts to understand why, after Khordad 15, republican thought became the dominant discourse of the opponents of the Pahlavi regime and what were the different understandings of the concept of republic. The findings show that the failure of the The Second National Front (1939–1941), land reforms, and traditional class discontent, along with the influence of liberation theology, paved the way for the growth of republican thought. Islamists saw the republic as a people-centered system with freedom of parties and decentralization of power; the People's Mujahedin-e Khalq saw the republic as a tool for combating imperialism and exploitation; and the Fedayeen-e Khalq saw it as a stage in the transition to socialism in which concepts such as democracy and popular sovereignty had little place.

Keywords: republicanism, liberation theology, Mujahedin-e Khalq, Fedayeen-e Khalq, Islamic movements