NBC says Souter is retiring.

Late Update: NPR says they broke the story. An email release says Nina Totenberg had the exclusive at 9:36 PM. "Totenberg reports that Souter is expected to remain on the bench until a successor has been chosen and confirmed, which may or may not be accomplished before the court reconvenes in October."

Later Update: Republicans were in such a good place. This should make them feel even better ... More seriously, this is a very bad development for the GOP; and quite a good one for the Democrats. Republicans had to hope this opportunity would come at a moment when Obama wasn't quite as popular as he is at this moment. What will he do with the opportunity?

Convo Update: Join the conversation in our Souter retirement discussion thread.