Howard Dean (search) argued, flattered, cajoled -- all to no avail.

In a lively radio debate Friday, the former Democratic presidential candidate tried to get Ralph Nader (search) to abandon his long-shot White House bid. Nader, the man Democrats blame for George W. Bush's election in 2000, declined and vowed to continue his independent campaign.

"Ralph, I think you're being disingenuous about your candidacy this year, and let me tell you why," Dean began at start of the debate. "Forty-six percent of all your signatures to get you on the Arizona ballot turned out to be Republican supporters. You accepted the support of a right-wing fanatic Republican group that's anti-gay in order to help you get on the ballot in Oregon."

"This is not going to help the progressive cause in America," said Dean, who has been urging his supporters to stay within the party and vote for Democratic presidential candidate John Kerry.

Nader quickly dismissed the criticism, telling the studio audience that Dean was engaging "in a desperate attempt to smear our campaign."

The former Vermont governor then tried flattery.

"You have an extraordinary career in standing up for the American people. You have saved lives with your extraordinary work with automobile safety," Dean told the consumer advocate. "I wish you were on our team, Ralph, because we really need you."

Nader again was unmoved and promised not to surrender for the sake of his supporters.

There were some lighter moments during the hour-long debate, which was sponsored by National Public Radio's "Justice Talking" program.

Nader drew laughter when he called Dean "an insurgent who is now adopting a role of being a detergent of the dirty linen of the Democratic Party (search)." Even Dean chuckled over that remark.

The crowd also roared when Dean was asked if would accept a Cabinet position in a Kerry administration. Dean said he hadn't "made any deals like that, but if Ralph comes on board maybe we can both get Cabinet positions."

Since Nader announced his campaign in February, Democrats have beseeched him not to run. Many Democrats blame him for taking votes from Al Gore in such razor-thin states as Florida and helping ensure Bush's victory in the 2000 election.

Nader has yet to make it on any state ballot independently. He has been endorsed by the national Reform Party, which has ballot lines in seven states, including the battlegrounds of Florida and Michigan. He was rebuffed by the Green Party when it declined to endorse him last month.

Click in the video box near the top of this story to watch a report by Fox News' Catherine Herridge.