It's official. Al Gore has endorsed Howard Dean for President:

Gore said Dean "really is the only candidate who has been able to inspire at the grass-roots level all over the country." He said the former Vermont governor also was the only Democratic candidate who made the correct judgment about the Iraq war.

"Our country has been weakened in its ability to fight the war against terror because of the catastrophic mistake the Bush administration made in taking us into war in Iraq," Gore said.

Gore is flying with Dean to Iowa today to campaign there. The AP describes the effect of Dean's endorsement this way:

The approval of Bill Clinton's No. 2 bolsters Dean's case that he can carry the party's mantle in November and represents more than an Internet-driven outsider relying on the support of largely white, upscale voters.

Joe Lieberman appeared on the Today Show this morning and said Gore's move "caught him completely off guard." And he got in one dig at Gore:

Asked on "Today" whether he felt betrayed by the former vice president, Lieberman said, "I'm not going to talk about Al Gore's sense of loyalty this morning."

Update: Here's the story on the secret plotting behind the endorsement.

Update: A new cnn/gallup poll shows Dean ahead in the Democratic race for the first time.

Twenty-five percent of registered voters who identify with or lean to the Democratic Party say they are supporting Dean for the nomination. Retired Gen. Wesley Clark ranks second with 17 percent. Three weeks ago, Dean and Clark were tied at 17 percent." [link via Political Wire.]

Update: Lieberman fights back.