and it hurts me to do it, but Andy's still being mostly sensible about Santorum so I'll link to him.
One thing he brings up is Santorum's criticisms of JFK for separating his faith from his politics. This kind of thing drives me batty. It really wasn't that long ago when American catholics were indeed a second class minority, both due to their religion and the fact that they were part of more recent waves of immigration to the U.S. Catholic politicans were accused of being more loyal to the pope than to the constitution. Historically, catholics were some of the staunchest defenders of the wall between state and religion, and the harshest critics of things like religious involvement in public education, precisely because they did have minority status and weren't too thrilled with the prospect of being told how to worship by a bunch of Protestants.
Of course, Rick Santorum probably is one of those catholics who doesn't think too much of the Pope, so maybe he isn't too worried about the loyalty charge. Santorum supports the death penalty, supported the war in Iraq, belongs to a church which has ignored the Vatican II reforms, has praised Opus Dei, an order which forbids giving alms to the poor, and has criticized Catholic Charities for not being Catholic enough.