I personally think that Al Gore will not endorse any of the candidates this time around, mostly because he wants to be in a position to work with the next President in 2009, and also partly because his endorsement of Howard Dean back in 2003-4 did not work out the way he would have wanted.
Nevertheless, I think it's interesting in the context of the current race to look back at what Gore said when he endorsed Howard Dean on December 9th, 2003:
"I've spent a long time thinking about national security and national defense, and I've heard a lot of folks, who in my opinion made a judgment about the Iraq war that was just plain wrong, saying that Howard Dean's decision to oppose the Iraq war calls his judgment on foreign policy into question.
"Well, excuse me.
He was the only major candidate who made the correct judgment about the Iraq war.
"And he had the insight and the courage to say and do the right thing. And that's important ...
... because those judgments, that basic common sense, is what you want in a president. "Our country has been weakened in our ability to fight the war against terror because of the catastrophic mistake that the Bush administration made in taking us into war in Iraq. It was Osama bin Laden that attacked us, not Saddam Hussein.
"Saddam Hussein is a bad guy and he's better off not in power. We're all better off. But it was a mistake to get us into a quagmire over there.
"So don't tell me that because Howard Dean was the only major candidate who was right about that war, that that somehow calls his judgment into question on foreign policy."
http://transcripts.cnn.com/TRANSCRIPTS/0312/09/se.01.html