William B. Prendergast analyzes the relationship between Catholics and the GOP from the 1840s to 1990s. He documents a developing attachment of Catholics to Republican candidates beginning early in this century and shows that, before Kennedy, Catholics helped elect Eisenhower, returned to the polls in support of Nixon and Reagan, and voted for a Republican Congress in 1994. To account for this shifting allegiance, Prendergast analyzes transformations in the Catholic population, the parties, and the political environment. He attributes these changes to the Americanization of immigrants, the socioeconomic and educational advancement of Catholics, and the emergence of new issues. He also cites the growth of ecumenicism, the influence of Vatican II, the abatement of Catholic-Protestant hostility, and the decline of anti-Catholicism in the Republican party. Clearly demonstrating a Catholic move toward political independence, Prendergast's work reveals both the realignment of voters and the influence of religious beliefs in the political arena. Provocative and informative, it confirms the opinion of pollsters that no candidate can take the vote of the largest and most diverse religious group in the nation for granted.