The religious scene in Mexico at midcentury was characterized by four broad developments, which would also be evident into the next century: gradual rapprochement between the Catholic Church and the government after a century of perennial antagonism, institutional consolidation and ideological flux and retrenchment within the Catholic Church, the maturation of historic Protestant churches and institutions and the strengthening of younger Pentecostal ones, and the intensification of migratory currents (back and forth) between the United States and Mexico. In the ensuing decades, the governing Partido Revolucionario Institucional (PRI) that emerged out of the revolution (1910–17) would see its authority weakened by corruption; student, guerrilla, and protest movements; controversial macroeconomic policies; and natural calamities. Mexico entered the twenty-first century a different country, with the Catholic-inspired Partido de Acción Nacional (PAN) heading a competitive multiparty system. The loss of PRI hegemony paralleled a relative but smaller decline in the percentage of Mexicans who identified as Catholic in an increasingly pluralistic society. The following thematic and chronological discussion of these developments will focus largely on the religious tradition with which nearly 80 percent of Mexicans still identified, at least nominally, in the 2000 national census, Roman Catholicism. Many of the twentieth (and nineteenth) century’s conflicts over religion, society, and governance were intra-Catholic affairs, pitting liberal, anticlerical Catholics against their conservative coreligionists.