Democratic presidential candidate Joe Lieberman (search) is trying to boost his campaign by tearing down Howard Dean (search) and, in doing so, capitalize on two surprises - losing an old ally and finding an old enemy.

In his sharpest criticism yet of Dean, Lieberman said Tuesday that the former Vermont governor's comment that "the capture of Saddam has not made America safer" raises the specter of a Democratic Party weak on national security.

"He thinks we're not safer by removing a homicidal maniac," Lieberman said in a speech. "The fact is that Governor Dean has made a series of dubious judgments and irresponsible statements in this campaign that together signal that he would take us back to the days when we Democrats were not trusted to defend our security."

The Connecticut senator has asserted for the past week that former Vice President Al Gore's endorsement of Dean has energized his own campaign. He was Gore's running mate in the 2000 campaign.

Lieberman now argues that Saddam Hussein's capture further highlights his strengths and Dean's weakness.

Lieberman is trying to jolt a static campaign by casting himself as the starkest alternative to Dean, who enjoys a wide lead in New Hampshire six weeks before the state's Jan. 27 presidential primary.

"To me, this race has crystalized between Howard Dean and me," he said.

Asked to comment, Dean, who was rallying supporters in Phoenix on Tuesday, said, "I'm not going to respond to Joe Lieberman."

But Lieberman said it's Dean who is focused on the negative, with foreign and domestic policies that would erode national security and cost millions of jobs.

"He seems to believe if you are just against everything, that's enough. Against removing Saddam Hussein (search), against middle-class tax cuts (search), against knocking down the walls of protection around the world so we can sell more products made in America," Lieberman said. "Dr. Dean has become Dr. No."

Lieberman, who was in single digits in the most recent survey of New Hampshire voters, contrasted his decade of service on the Senate Armed Services Committee with Dean's opposition to the Iraq war and his statement last spring that the United States won't always have the strongest military.

"More than anyone in this race, I am prepared to lead America to the war on terrorism. I will rebuild our fractured alliances and rally the international community," Lieberman said. "And I will use whatever force is necessary to kill those who would kill us, as we have done and are doing."

Rep. Dick Gephardt (search) of Missouri, another contender for the Democratic nomination, also criticized Dean in a conference call with reporters Tuesday. Gephardt said Saddam's capture and Dean's comments "make one thing pretty clear. And that is a candidate with no foreign policy experience is not going to beat George Bush."

On domestic issues, Lieberman said he wants to cut taxes on the middle class and small businesses and expand trade while Dean wants to raise taxes, impose new regulations on businesses, and rebuild trade barriers.

"That would start a trade war and cost millions of Americans their jobs," he said. "The man who didn't want to fight a war we should have fought now wants to start a war we shouldn't start."