My paper gives a brief genealogy of the “political theology” of the Muslim Brotherhood from its founding to when Mohammed Morsi took power on June 24, 2012 in Egypt, focusing on how the group has leveraged a religiously-inflected rhetoric of “authenticity” to advance its political aims. Compared to religious political groups to the “left” of the Muslim Brotherhood, including the current leadership of Al-Azhar, the Muslim Brotherhood continues -- despite challenges that are deepening as we speak -- to dominate populist religious rhetoric in Egypt. I argue that the Muslim Brotherhood in Egypt, founded by Hassan al-Banna in 1928, has enjoyed massive success as an opposition movement in large part through appeal to an “authentic” Islamic and pan-Islamic identity. Early in Egyptian history, by 1936, the Brotherhood took an official stand against British colonialism and coupled this opposition with a defense of traditional (Islamic) values against a liberalism ushered in starting in the era of the 1919 constitution. The Brotherhood characterized this social mood and its attendant reforms as a form of cultural imperialism. The Muslim Brotherhood’s reputation for “authenticity” is especially strong because of what we know of Hassan al-Banna’s influences, which include Muhammed Abduh and Rachid Reda, famous Muslim reformers of the late 19th and early 20th century al-Nahda (the awakening) era. Moreover, the Brotherhood’s rhetoric of both staunch opposition to Israel (declaring, for example, Al-Aqsa mosque a waqf) and willingness to soften that rhetoric in cases deemed necessary for Egypt’s security allowed them to sound both regional and domestic notes of authenticity. The question is whether the rhetoric of “authenticity” works in the current context of state power. There is evidence that attending Morsi’s ascent to power is a massive reduction in the pathos engendered by the rhetoric “authenticity”. If Egypt functions in a similar way to Northern Nigeria (which I examine in other work) after their 1999 sharia revolution – which is to say that the practicalities of governance and the persistence of Islamist self-interest caused those groups to lose credibility -- than I argue that the effectiveness of the Muslim Brotherhood’s use of the rhetoric of religious “authenticity” is tied to the group’s oppositional status. In the final analysis, I show -- “to oppose” in contemporary Egypt is the most authentic affect of all, and this “authenticity,” rather than outward displays of piety, is where the populist power actual lies.