Once Al Gore's running mate, the Connecticut senator lost his party's primary in 2006 over his support of the Iraq war.
His official portrait sits in a closet at the Connecticut Democratic Party headquarters in Hartford. Party elders have stripped him of his superdelegate cape.
And he is so disinterested in the Democratic presidential candidates-- though he counts both as friends -- that he declined to vote in his state's primary.
Sen. Joseph Lieberman of Connecticut, not so long ago the Democratic nominee for vice president, has become chief endorser, campaign companion and all-around champion for his buddy Sen. John McCain of Arizona, the presumptive Republican presidential standard-bearer.
So inseparable are these men lately that the question often arises: Would Lieberman consider another tilt at the vice presidential lists, this time on the Republican ticket?
A smile crossed his face like a cloud, and the white-haired senator began waving his hands.
"Oh, no, no," Lieberman insisted in an interview in his Capitol hideaway, a nook that he occupies between votes and that once belonged to none other than McCain. "Been there, done that."
This is the latest steeply graded curve in the long, strange trip that is Lieberman's career. Eight years ago he exhorted sweaty ironworkers in Boynton Beach, Fla., to join the Democratic cause. Four years ago he told voters in New Hampshire that President Bush was "a divisive leader."
But a month ago he returned to Boynton Beach to address 250 Republicans at a country club. This time, he deplored the Democrats' "visceral" anger at Bush. And he is skipping the Democratic National Convention in Denver -- but may well turn up at the rostrum of the Republicans' conclave in St. Paul.
"I suppose if Sen. McCain is going to be nominated, and he asks me, I will go," Lieberman said.
He is technically an independent, ever since he lost his own primary in 2006 in the face of voter opposition to his championing of the war in Iraq. But he caucuses with Democrats in the Senate, in trade for the seniority privileges and committee chairmanship that accompany that party identification. In a Senate nearly evenly divided, even one senatorial defection would shift the balance of power.
Thus far, his endorsement of McCain in December, when the polls had him as a long shot, has paid off like the daily double at Belmont. He has garnered attention and, as yet, paid no price in power or prestige.
But he has not amused his fellow Democrats, particularly in Connecticut, where many affect stony silence or ask to go off the record, the better to share their not-fit-for-a-family-newspaper assessment of this apostate.
"Look, I didn't figure he was likely to go to the Democratic convention this year because someone would have gotten in his face," said Nancy DiNardo, Connecticut's Democratic Party chairwoman, who is often called upon to deconstruct the life and times of this sort-of Democratic senator of hers.
The party revoked Lieberman's superdelegate privileges under what is known as the Zell Miller rule. Somewhat unbelievably, the Democrats faced a similar situation in 2004, when Miller of Georgia, then a sitting senator of their caucus, gave the keynote speech at the Republican convention.
As for Lieberman's portrait, DiNardo said: "When he endorsed, that picture came down."
For the longest time, Lieberman was a regular Democratic Joe. He clambered up the party ladder, serving as state attorney general before taking a Senate seat in 1988. Bill Clinton and Hillary Rodham volunteered in an early campaign while at Yale Law School ("It was more Bill," Lieberman recalled. "Hillary was too studious to take time off; he wanted to do politics.")
He flapped like a hawk on foreign politics and sang like a moderate bird on domestic affairs. He annoyed the White House when he denounced Clinton's conduct in the Monica Lewinsky affair, but he voted against impeachment.
In 2000, Al Gore tapped him for the No. 2 slot. Lieberman did not flash the dirk as often as Gore aides preferred, and he went curiously passive in Florida, when the election hung in the balance. But he worked the trail as if plying the tables at Grossingers, the Catskill resort hotel. "Have you heard our campaign slogan?" he would tell the crowds. "Gore-Lieberman: No Bull, No Pork."
Later he become a mentor to Sen. Barack Obama of Illinois, sharing lunches with the freshman. Their offices are 148 feet apart.
In 2004, Lieberman alighted in New Hampshire as the presidential candidate with the broadest name recognition. But voters criticized his support for the war in Iraq, and he lectured them, and this did not go well. He finished fifth and soon folded his tent.
Bill Curry, an adviser in the Clinton White House who once sat alongside Lieberman in the Connecticut state Senate, had lunch with Lieberman in December 2005 and warned about the antiwar sentiment sweeping Connecticut.
"This is not an argument over the capital gains tax," Curry recalled telling him. "This is the biggest foreign policy mistake in the history of the country."
Lieberman, who often praised Donald Rumsfeld, the defense secretary at the time, shrugged off this advice. He saw the war as an epic struggle against Islamic terrorism; bombing Iran might not be a bad idea, either.
Ned Lamont, a businessman from Greenwich, Conn., mounted an improbable primary challenge and won, though Lieberman became an independent and bested him in a November rematch to keep his seat.
"I had some of my most profoundly disappointing moments in that election," he said. "In the end, I came out feeling profoundly liberated."