One thing that puzzles me about these numbers: Obama's progress among Catholics is with those who don't attend mass weekly. But among Protestants, he improved among those who do attend weekly.
One possible theory: abortion. Mass-attending Catholics are more likely to care about abortion than those who go less regularly. Protestant weekly attenders, on the other hand, include Mainline Protestants that are not necessarily pro-life.
But that's just a theory. Based on very preliminary exit polls.
(Originally posted at Steve Waldman's blog at Beliefnet.)