I live in predominately Catholic area. It's basically the last Republican stronghold in New York City (although we will probably send a Democrat to this coming Congress, as our current Republican Rep. found himself in scandal). But it seems to me like most Catholic members of Congress are Democrats. Or at least the more prominent ones. Why is that?
Catholicism has historically been associated with the Democrats. The reasons for that are very far in the past, but have to do with the fact that the Republicans upon their founding absorbed a good part of the American Party.