This paper examines how the evolution of ideational conflicts between Islamist and leftist intellectual advocates over the past four decades has shaped the dominant discourse and narrative through which leftists have sought to justify the repression of Islamist currents in the aftermath of the 2013 coup. The paper builds its argument on an analysis of a variety of primary sources, including books and articles published by leftist and Islamist intellectuals since the 1970s. Since the mid-1970s, debates and conflicts between Islamist and leftist intellectuals and activists have generated a variety of historical narratives and a repertoire of language that endorsed the political exclusion of ideological rivals. The 1970s and 1980s saw the advent of an Islamist “authenticity critique” of the left. That critique argued that leftist movements do not enjoy an organic connection with Egyptian society, presenting them as foreign implants with questionable national loyalties. In making these arguments, Islamist critics often invoked historical narratives underscoring the pivotal contributions of foreigners to the creation and advancement of the communist movement. The political victories of the Muslim Brotherhood in the late 1980s and Islamist attacks against secular intellectuals in the 1990s, paved the way for a leftist counter-critique of Islamists, one that continues to shape leftist discourse in the contemporary moment. Adopting a strong nationalist veneer, the counter-critique held that it was the Islamist movement that lacked authentic roots in Egyptian society, while arguing that Islamists’ loyalties lie not with Egypt, but with international networks of Islamist groups and governments. Supporting that counter-critique was an effort to construct a historical narrative of Egypt’s Islamist movement that imbues it with an un-Egyptian, anti-nationalist character and, relatedly, alleges its tacit commitment to violence. In situating this historical context, the article brings to light new lines of inquiry about the historical origins of political polarization in post-Mubarak Egypt, and important junctures that contributed to this phenomenon.