What factors underpin the "Islamist Advantage" at the ballot box? We argue that an embedded, nationwide infrastructure of mosques disproportionately benefits Islamist candidates while disadvantaging their non-Islamist competitors. We support for the theory through a variety of original spatial data, coupling geolocated ballot-box level election returns from Egypt's first presidential elections with web-scraped data on the country's Muslim and Christian religious infrastructure. We find that, at the level of the individual ballot box, both mosque proximity and mosque density were powerful predictors of electoral success for Muslim Brotherhood candidate Mohammed Morsi. Further, the proximity and density of churches were similarly-powerful predictors of success for Morsi's opponent, former Mubarak Prime Minister Ahmed Shafiq. Together, these findings emphasize the importance of considering the local ecologies of electoral mobilization, and suggest the promise of spatial methods to understand political outcomes in the Middle East.