This seemed like a pretty foregone conclusion based on all of yesterday's leaks and chatters, but at his lunchtime press conference today in Stamford, CT, Joe Lieberman just made it official: he will not be running for a fifth term in the Senate.
"I have decided it is time to turn the page to a new chapter, and so I will not be a candidate for re-election..."
"I promised [my wife] that when Regis leaves television, I'll leave the Senate."
The exit of Lieberman, who had many different ways of approaching the 2012 Senate race but probably no way of winning it, makes things easier for the Democrats here, turning this into a very straightforward two-way instead of a hard-to-game three-person race. Whether that Dem nominee will be Chris Murphy, Susan Bysiewicz, or somebody else... that's the new big question in Connecticut.
UPDATE: If you haven't seen it, here's an excellent overview of Lieberman's rise and fall, from Salon's Steve Kornacki, who as always knows his history. Our younger readers may not be familiar with Lieberman's first election in 1988, which he won by running to the right of iconoclastic Republican incumbent Lowell Weicker.