Here are basics, but read Mark Silk's take on the designation of Miguel H. Diaz, professor of theology at St. John's University and the College of Saint Benedict in Minnesota as the United States' ambassador to the Vatican.
For starters, with Sotomayor this makes for a serious one-two punch with Latinos. It's very interesting that he's a theologian rather than your basic Catholic pol or lawyer type. ... This strikes me as the shrewdest of moves, and one that will cause no end of teeth-grinding on the Catholic right, including the likes of Archbishop Burke. But we await learned commentary from his co-religionists.
Update: Turns out Diaz is a consultant to Catholics in Alliance for the Common Good. Big win for social-justice, common-ground Catholics.
Exegesis: Catholic conservatives would be free to rail against a pro-Obama Catholic politician. "Not a real Catholic," etc. A pro-Obama Catholic theologian who teaches at a major seminary, well, that's a different story. And the fact that he's a Latino working on issues in Hispanic theology, at a time where we're experiencing the Latinization of the American Catholic Church--that's a ten-strike.
And more Silk. Same topic.