And it's also no secret that Lieberman was stung when he failed to win the Democratic nomination for re-election run in Connecticut last year, shunned over his support for the war. He went on to successfully run as an independent. Lieberman now calls himself an "independent Democrat" and still caucuses with Democrats, who, with a one-vote margin in the Senate, welcome him.
But what will a Lieberman endorsement do for McCain, particularly in New Hampshire, where the Arizona senator's presidential campaign could expire if he doesn't make a strong showing in that state's January 8 primary?
"It certainly doesn't hurt; it's another log on the fire," said New Hampshire GOP chairman Fergus Cullen. "It may help among the state's independents," who are eligible to vote in party primaries. (McCain over the weekend also picked up endorsements from the Des Moines Register, the Boston Globe, and two New Hampshire newspapers.)
More than 44 percent of New Hampshire's voters are not registered in a party, and these are the people who gave McCain his Granite State primary win in 2000. Polls early this year, however, showed that 38 percent of independent voters in New Hampshire said they would not, under any circumstances, vote for McCain. And in April, 72 percent of independents said they planned to vote in the Democratic primary.
But the ground has shifted considerably in recent months. A New Hampshire poll last week found that 54 percent of independent voters say they'll mark a Democratic ballot, and 46 percent are planning to vote for a Republican. And with more than half of all the state's voters still undecided, endorsements captured by McCain over the past few days--including Lieberman's--could help put his resuscitated campaign within striking distance of leader Mitt Romney. (Polls show McCain rising to second in New Hampshire as Rudy Giuliani fades, but Romney is holding steady with a 13-point lead.)
History shows that Granite Staters don't have any particular affinity for Lieberman. When the 2000 Democratic vice presidential nominee made his own bid for the presidency in 2004, he finished a distant fifth in the state's primary, with less than 10 percent of the vote. He picked up about 12 percent of the independent vote. Winner John Kerry captured 36 percent and second-place finisher Howard Dean got 25 percent.
"We're not sure" what Lieberman's decision to cross party lines will mean, says Ray Buckley, chair of New Hampshire's Democratic Party. "This is a year where so many possibilities exist both in Iowa and New Hampshire that nobody's sure about anything.
"But," he said, "there are precious few independents who are pro-Bush war."
By Liz Halloran