Blogger emeritus Peter Nixon in Commonweal:

It is hard to escape the conclusion that the distinct voice that Catholics once brought to the public square is gradually being lost. In its place, we see the emergence of two separate Catholic political cultures, each serving the needs of one of the two major parties, and each with its own “magisterium.” Those wishing to embrace the church’s social-justice tradition while evading the moral force of its teaching on abortion can cite the speeches of Mario Cuomo, while those seeking a Catholic apologetics for libertarian economics or preemptive war can consult the encyclicals of Michael Novak and George Weigel.

The fact that Catholics are divided between the two parties is not the problem. There is no reason why Catholics must be of one mind on all matters of public policy. But there is still something disturbing about seeing Catholics become so completely conformed to the ideologies of their chosen political parties or movements. The recanting of earlier prolife views by so many prominent Catholic Democrats is one example of this. The unwillingness of many Catholic Republicans to offer any criticism of the Gonzales nomination-to say nothing of the war in Iraq-may be another.

Seems to me much the same could be said of Protestants, except it tends to break down along evangelical/mainline lines with the former tilting heavily towards the GOP and the latter towards the Dems.