[cnn-photo-caption image= http://i2.cdn.turner.com/cnn/2008/images/08/20/art.liebermanconvention.ap.jpg caption="Democrat-turned-Independent Lieberman will speak during the opening night of the GOP convention."]
WASHINGTON (CNN) - Connecticut Sen. Joe Lieberman, the 2000 Democratic vice presidential nominee, will speak on Sen. John McCain’s behalf at the Republican National Convention, a source in the McCain campaign tells CNN.
Lieberman, who became an Independent in 2006 after losing the Democratic primary in his Senate re-election bid, has been a high profile surrogate on the campaign trail for McCain, the presumptive Republican presidential nominee.
Lieberman, who won re-election to his Senate seat, hinted earlier this month what tone he would strike at the convention being held next month in St. Paul.
"I'm not going to go to that convention, the Republican convention, and spend my time attacking Barack Obama,” Lieberman said in an interview on NBC’s Meet the Press. “I'm going to go there really talking about why I support John McCain and why I hope a lot of other independents and Democrats will do that. And frankly, I'm going to go to a partisan convention and tell them, if I go, why it's so important that we start to act like Americans and not as... partisan mudslingers here in Washington."
While Lieberman is campaigning on behalf of McCain, he has not cut all ties to the Democratic Party. This year, he donated $115,000 to the Democratic Senatorial Campaign Committee, matching what he contributed to the political arm of the Senate Democratic Caucus in 2007.
And he continues to be included in the Democratic head count that gives them the majority in the Senate by the slimmest of margins – one vote. In turn, Lieberman chairs the Homeland Security and Governmental Affairs Committee — a powerful perch with wide jurisdiction over the Bush administration.
Lieberman was first elected to the Senate as a Democrat in 1988 and 12 years later found himself standing alongside Vice President Al Gore, as Gore's running mate. Six years later, it looked like his political career had come crashing down. His support for the war in Iraq prompted businessman Ned Lamont to challenge him in the Democratic primary.
After losing the primary, Lieberman vowed to continue running, a decision that caused many prominent Democrats, including fellow Connecticut Democratic Sen. Chris Dodd, to endorse Lamont. The endorsements weren't enough to seal a victory for Lamont — Lieberman was elected to another term.