Though he lost the vice presidency in 2000, he returned to the Senate and never hinted at even a trace of dismay.

“ ‘You just lost an election. You didn’t lose your life, and you’ve got a lot of years ahead of you when you can do a lot of things,’ ” he recalled his mother saying.

“I’m not haunted by it,” he said. “Do I go back to it periodically and feel disappointed, frustrated, angry? Of course I do."

Work and faith were his salves, and this next chapter was arguably the most productive of his Senate career. As the chairman of the Senate committee that oversees homeland security, Lieberman led the fight, and worked closely with Republicans, to revamp the nation’s domestic anti-terrorist efforts and create the independent commission that investigated the Sept. 11, 2001, attacks.

The Bush administration resisted the commission. “We went up against the status quo and challenged the status quo,” Lieberman recalled, grinning.

Those triumphs were quickly clouded. His bid for the 2004 Democratic presidential nomination went nowhere, and he became the Democrats’ most visible supporter of the increasingly unpopular Iraq War. By 2006, even his home-state support had eroded, and he had a primary challenge for his seat from businessman Ned Lamont.

“I thought, ‘I’m a Democrat. I’ve been a Democrat all my life,’ ” Lieberman said. “I understand how strongly they want us to get out of Iraq quickly, but, you know, I worked so closely with so many Democrats, so I’m going to take this (Senate primary) on. . . . I’m not going to leave on my own.”

They did want to kick him out. He lost the primary on what he called “the most hurtful night of my career.”

That night also proved to be the beginning of a new, bumpier, chapter.

He ran for the Senate as an independent. “Election night . . . maybe I even felt better and more excited that night than I did the first night I got elected to the Senate,” he recalled, as he won easily.

Lieberman returned to the Senate a pariah of sorts. He caucused with Democrats. But by the time the 2008 presidential campaign rolled around, he felt the draw of his friendship with Sen. McCain, R-Ariz., and supported him, a stunning break for a man who’d been on the Democratic ticket just eight years earlier.

McCain reportedly came close to picking Lieberman as the Republican vice-presidential candidate before settling on Sarah Palin as more acceptable to his party’s conservative base.

.Lieberman praised McCain and Palin – and ripped into Obama – in his convention speech. “He has not reached across party lines to . . . accomplish anything significant, nor has he been willing to take on powerful interest groups in the Democratic Party to get something done,” he said of then-Sen. Obama.

“As I look back at it,” Lieberman said recently, “I wish I’d left those lines out. It wasn’t my purpose there.”

A lot of Democrats saw the speech as an act not of bipartisanship, but of treachery. Adding to Lieberman’s new world was a new kind of Senate, in which he wasn’t roundly embraced by either party and key legislation passed because Democrats and their strong majority stuck together, rarely reaching across aisles.

"There’s no middle anymore," Senate Historian Donald Ritchie said. "That’s why people like Lieberman are now seen as mavericks."

Lieberman leaves on a somber note. He delivered his farewell address Dec. 12, and while full of lofty recollections, he conceded that his quest for common ground remained unfulfilled.

"Today, I regret to say, as I leave the Senate," he said, "the greatest obstacle standing between us and the brighter American future we all want is right here in Washington."

He’ll be succeeded by Democratic Rep. Christopher Murphy of Connecticut, who in the most recent Congress voted with Democrats consistently.