After Manhattan District Attorney Robert Morgenthau announced his impending retirement last week, speculation began over who he might support to be his successor—either family friend and former ADA Cyrus Vance Jr. or current deputy DA and "righthand man" Dan Castleman. Well, now the cat is nearly out of the bag: Castleman offered his resignation yesterday, apparently because Morgenthau has chosen Vance.

Castleman has worked in the Manhattan DA's office for almost 30 years; Morgenthau has been DA for 35. One source told Post that Morgenthau allegedly offered Castleman his support but now, "Dan thinks Morgenthau screwed him" (another person called Morgenthau "Judas"). Guess Morgy didn't mind that Vance started his "Cyrus Vance for District Attorney" committee back in January!

Morgenthau, 89, tried to clear things up during a press conference today, saying that while he wasn't sure he could publicly support anyone, "It's a judgment call and I could be wrong. What is best for the office is not what is best for a personal friend." The Daily News thinks that Morgenthau's statement "being Mr. Inside and Mr. Outside are two different talents" suggests that Castleman is a great prosecutor but maybe not so good with the politics of it. The Post's sources say Castleman won't run for DA, setting up a potential Vance vs. Leslie Crocker Snyder showdown.

And why is the position such a big deal? Newsday's Dan Janison explained, "The Manhattan DA's office has been the pace-setter in the region regarding specially-funded state programs that affect district attorneys' offices -- a budgeting operation that court insiders say has impact on Nassau, Suffolk, and the city's other four boroughs."