The feature article in the current issue of Touchstone is worth checking out. My time is still limited this week, so I can't comment much, but give it a click:
There may be political explanations for the attractiveness of Catholic justices, but I think three Catholic doctrines–natural law, subsidiarity, and religious freedom–help to explain why a majority of the justices are now Catholic. My argument is not that citizens who support, presidents who appoint, and senators who confirm these justices consciously do so because they want Catholic religious beliefs on the Court, but that these doctrines yield habits of thinking that make Catholics attractive candidates to the broad range of the American people.
I write as an Evangelical, but one who has come to share a commitment to the Catholic doctrines that I will mention.