"And it's an important fight," the three-term Connecticut senator said as he struggled to turn back a surprisingly tough challenge from war critic Ned Lamont.
The former president wasn't the only nationally known Democrat campaigning for Lieberman as the lawmaker sought to rebuild support among Democrats who long supported him.
Sen. Barbara Boxer of California, an ardent critic of the war, praised Lieberman for his stand on other issues. "If you want to meet a leader on the environment, a leader on all the difficult choice issues, you got one here," she said at a campaign stop at a candy store.
Even then, Lieberman was looking forward to Clinton's visit.
"You know, I'm in a big fight here, and I understand that ... and as our mutual friend who's coming in later today, President Clinton, always reminds us, every campaign is about the future," he said.
The most recent public poll rated the race a tossup with the wealthy Lamont, whose Web site boasts that he will give Connecticut, "finally, a senator who will stand up to George Bush."
Lamont countered with endorsements of his own during the day. His office said he had gained the support of Carl S. Feen, the finance chair of Lieberman's first campaign and a former Clinton appointee.
Irving Stolberg, two-term speaker of the Connecticut House of Representatives in the 1980s, also swung behind Lamont, a Greenwich, Conn., businessman who made millions in telecommunications. His political experience is limited to two years as a Greenwich selectman from 1987-89 and six years on the town's Board of Estimate and Taxation from 1989-95.
Lieberman has filed petitions to run as an independent if he loses the Aug. 8 primary to Lamont, although it seems likely he would come under heavy pressure from party leaders to reconsider his plans.
Clinton has said he will support the winner of the primary in the fall campaign, and it would be highly unusual if the Democratic Senatorial Campaign Committee and Democratic National Committee didn't follow precedent and do the same.
There was irony in Lieberman's decision to call on Clinton.
Once, the senator gained national prominence for criticizing the president on the Senate floor over his relationship with White House intern Monica Lewinsky.
That led to Lieberman's selection as Al Gore's vice presidential running mate in 2000.
Lieberman ran for president four years later, and defended his decision to work across party lines in the Senate. He fared poorly in the early nominating contests and dropped out of the race.
Now, his horizon has shrunk to his home state, and his votes in support of the Iraq War have helped energize Lamont and the rank-and-file Democrats eager for a change.
Democratic strategists have said Lieberman awoke belatedly to the severity of the challenge, and in recent weeks, he has tried to regain the offensive.
"I know George Bush. I've worked against George Bush. I've even run against George Bush. But Ned, I'm not George Bush," Lieberman said recently during the only debate of their campaign.
"So why don't you stop running against him and have the courage and honesty to run against me and the facts of my record."
Lieberman also brought in fresh help to organize a get-out-the-vote operation, fearful that previous efforts were insufficient.