This article examines the origins of the unlikely alliance between Donald Trump and evangelicals, a relationship that defines the modern-day Republican Party. Using 2016 Cooperative Congressional Election Study data, I explain how Trump ultimately succeeded among this critical group of Republican primary voters in the contest for the 2016 presidential nomination by exploiting key internal divisions. Trump initially performed well among less educated evangelicals who were less devoted to their religion and less ideologically conservative. Contrary to previous research, I find that Texas senator Ted Cruz's core support among the traditional Christian Right-very conservative, churchgoing evangelicals-resisted Trump until the late stages of the nomination contest. However, Cruz was unable to expand his support among his co-religionists, despite his evangelical identity. Trump's success among evangelicals speaks not only to the oft-cited importance of momentum in presidential nomination contests, but also to the significance of candidate ideology to primary voters, especially when paired with religiosity.