Lieberman's attack, leveled one day after Clark escaped criticism in his first debate, underscored how quickly campaign strategies are shifting in the wake of two political phenomena: Clark's burst upon the crowded scene Sept. 17 and Howard Dean's front-running, Internet-driven campaign.
Dean, a former governor of Vermont, was criticized over several issues in Thursday's debate while Clark was largely given a pass. The day after, Lieberman took issue with Clark expressing support for the Bush administration's policies in a May 2001 address to the Arkansas GOP.
"I was fighting (Bush's) reckless economic strategy while Wes Clark was working to forward the Republican agenda by raising money for the Republican Party," the Connecticut senator said.
Clark spokesman Mark Fabiani fired back: "I think Senator Lieberman is an increasingly desperate candidate and it's unfortunate that instead of articulating a vision for the future as General Clark has with his 'New American Patriotism,' Senator Lieberman is attacking other Democrats."
Lieberman's criticism suggests that he sees Clark as a direct threat, particularly in New Hampshire's primary where both are courting independents and conservative Democrats. Independents can vote in the state's Democratic primary.
"It shows you we now have a primary within a primary, between Clark and Lieberman for the center wing of the Democratic Party," said David Corbin, political science professor at the University of New Hampshire. "What you're going to see is Lieberman resting on his laurels as a conservative Democrat with centrist philosophies and Clark resting on his laurels of his (military) stripes, his military record — believing that his resume rather than philosophy will win over centrist voters."
A new poll has Dean, Sen. John Kerry of Massachusetts and Clark as the top three in the New Hampshire field. Joe Keefe, a Kerry backer in New Hampshire, said that while Kerry and Dean continue to battle, the rest of the field must decide whether to criticize Dean or turn first to Clark.
"Clark's candidacy has forced all of us to look at this race differently," Keefe said.
His momentum has caught the attention of Republicans. House Speaker Dennis Hastert, R-Ill., criticized Clark's plan to repeal portions of President Bush's tax cuts that favor the wealthy.
"When Wes Clark says he wants to raise taxes on those who make more than $200,000, he is actually saying that he wants to raise taxes on job creation," said Hastert, who did not mention Clark's rivals who have long been pushing a similar proposal.
Lieberman's criticism underscores a potential vulnerability for Clark, who had not publicly embraced the Democratic Party until days before entering the race. Democratic caucuses and primaries are dominated by liberals and other voters angry with President Bush. It is unclear how they will react to Clark praising former President Reagan, the first President Bush and the current Bush administration in the 2001 speech.
Clark also seemed to raise doubts about whether the Clinton administration had a foreign policy vision in the address.
"I think they'll nab him on all that stuff, including being a Republican. The honeymoon will soon be over for Clark," said Democratic National Committee member Anita Freedman, a New Hampshire activist who supports Rep. Dick Gephardt's campaign.
Some Democrats said that by criticizing the former general, Lieberman and his rivals risk underscoring what Clark views as his strength — political independence that may appeal to voters eager for a candidate who can defeat Mr. Bush.
"By saying, 'Democrats, watch out for this guy!' is like saying, 'Hey, independents, watch this guy!"' said former Democratic strategist Dayton Duncan, author of a book on the 1988 New Hampshire primary.
Instead of hiding his GOP past, Clark is embracing it. At a post-debate fund-raiser, he called himself "the newest Democrat in the room" and vowed to bring millions of new voters into the party's fold.