Yup, it's official. Marty's backing Bloomberg. Everybody's got it. City Hall News with the (really really early) preview announcement, Ben Muessig with the Brooklyn Paper for the breaking, and Cobble Hill Blog's Diana Rosenthal has more... and that's it.
As one council source told me, Marty likes winners. He backed Steve Levin, David Yassky (edit, hold on, erasing), and a mission to Burma of some kind.