Howard Schweber explains:
[T]he "Catholic" political style is strongest among evangelical Protestant voters, not actual Catholics. The eagerness of Catholic bishops to jump into a fight over contraception, for example, does not reflect that attitudes of their parishoners, but it gets strong support from evangelicals. Similarly, in one recent poll more than two-thirds of Catholic voters supported some sort of legal recognition of gay couples' relationships, with 44% favoring same-sex marriage; in very sharp contrast, an outright majority of evangelical voters said there should be no legal recognition of a same-sex relationship.
In political terms, the evangelical Protestant Right has become Catholicized. They do not see Catholicism as a religion very different from their own because it leads to the same positions on the battlefield, call it Fortress GOP. It is a political worldview that is singularly well suited to negative politics. Who cares whether your guy is actually a bit of a nut-case or has some sleaze in his history if he will defeat the forces of darkness? Liberals tolerate venality in their candidates if they believe they will do good; "Catholic" conservatives tolerate venality if they believe their candidates will defeat evil.
As Glenn Beck said last week, "we are all Catholics now." Which means: we are all for Republicanized religion as politics.