All the bloggers I read are so busy finding deep meanings in the Gore endorsement of Dean that they don't give enough weight to the obvious aspects of the timing. The past 7-10 days of the Democratic contest have seen the candidates begin to go overtly negative about each other, even in TV ads. That helps Bush and hurts the eventual nominee whoever he is.
If you are Al Gore, the thing you want most out of this next election is for Bush to lose. Preferably to lose big. If Bush were to win, it could have some retrospective legitimating effect on the 2000 election. If Bush loses, and especially if he loses big, history will be brutal. If I were Gore that is what I would most want.
By endorsing now, Gore helps cement Dean's frontrunner status and cuts down on (nothing short of a Clinton endorsement can eliminate) the internecine sparring that is grist for the Republican mill in the general election. That's canny. It's also statesmanlike.
The only part of this I don't understand is the failure to make at least a courtesy call to Lieberman. One would think he was owed that, unless there is some hidden bad blood somewhere. Lieberman was not very helpful to Gore during the period after the election, while Florida was in doubt, and perhaps that has something to do with it?