What has caused the religious polarization of Brazilian politics? And do the “culture wars” threaten or shore up democracy? The Introduction outlines the book’s argument. It then introduces the religious groups who are the protagonists of the story: evangelicals, Pentecostals, and Catholics. Brazilians in all demographic groups—men and women, young and old, in all regions of the country—have since the 1970s been leaving Catholicism and converting to evangelicalism and Pentecostalism. In response, non-Pentecostal religious groups have become “Pentecostalized,” adopting aspects of Pentecostalism. The chapter then considers the religious activism of these groups since Brazil’s return to democracy in 1985. While the Roman Catholic Church has largely avoided electoral politics, it has been active in promoting theological/political objectives such as support for religious education opposition to abortion. Meanwhile, evangelical and Pentecostal leaders have adopted a corporatist strategy that involves promoting ingroup candidates in elections.