Mark, I’m curious about those numbers, too. Why would Obama garner more support than McCain from Roman Catholics?
Partly because there is still anger at the Republican Party for the despicable way that they treated Catholics in the 1800s and 1900s, and partly because Catholics listened to more than the abortion message - many of them fell for the Democratic platform one more time.
However, if you look at the numbers between 2004 and 2008, Catholics moved towards the Democrats by about the same percentage as the Protestants did - it is just that the Protestants stayed just under 50%, while the Catholics moved just over 50%.
Catholics are making the trends toward the Republican Party with strong Christian values - I introduce in evidence the fact that Catholics are 67% of SCOTUS and Protestants do not occupy a single chair. And all were appointed by Protestant Presidents. Are you curious, yourself, about that? :)