Washington ? John Kerry and John Edwards swapped charges as their South Carolina primary fight shaped up to be key to Kerry’s dreams of sweeping seven states today and seizing command of the Democratic nomination fight.

On the eve of a cross-country contest, Howard Dean joined Edwards in calling the front-runner a friend of special interests. But there were fresh signs of weakness in Dean’s campaign, and Kerry went for the jugular against Edwards, questioning the North Carolina senator’s credentials and electability.

“This is not the time for on-the-job training,” Kerry told South Carolina reporters Monday via satellite from Albuquerque, N.M. In a speech, the four-term Massachusetts senator looked confidently beyond the nomination fight to a potential race against President Bush.

“Like father like son. One term only,” Kerry said. “Bush is going to be done.”

Though they would agree with that point, Kerry’s chief rivals said he was not the candidate best suited to stand up to Bush.

“It’s going to take one tough hombre,” Wesley Clark said while courting Hispanic voters in New Mexico. “And I’m one tough hombre.”

Clark, Edwards, Dean and Sen. Joe Lieberman faced long odds trying to slow Kerry’s momentum. Polls showed him with solid leads in Missouri, Arizona, New Mexico, Delaware and North Dakota. Kerry was within reach of victory in the remaining two states, South Carolina and Oklahoma.

In South Carolina, where Edwards needs to eke out a victory to keep his candidacy alive, election officials dropped the requirement for voters to sign an oath binding them to the Democratic Party. Strategists said the decision could increase turnout of black voters, a bloc trending toward Kerry, because oaths carry a stigma of times past when poll taxes and literacy tests were used to keep minorities from voting.

The move also could benefit Edwards, who, according to polls, attracts South Carolina’s independent voters, the strategists said.

Democratic presidential hopeful John Edwards, right, greets supporters before addressing an audience during a campaign stop at a family center, in Seneca, S.C. Edwards campaigned on Monday, ahead of today's primaries in South Carolina and six other states.

Edwards, who has promised to run a positive campaign, criticized Kerry’s acceptance of contributions from lobbyists and his free-trade policies.

“I don’t take contributions from lobbyists, and he obviously does,” Edwards said after a speech at the College of Charleston. “If we want real change in Washington, we need someone who hasn’t been there for 15-20 years.”

Holly Armstrong, press secretary for Kerry in South Carolina, said it was ironic that Edwards, a wealthy trial lawyer, “is launching an attack on special interests when the majority of his money comes from one interest group.”

Dean, who just three weeks ago was considered the race’s front-runner, has not advertised in the seven states voting today. He also decided against advertising in Michigan, the delegate-rich state holding caucuses Saturday. And he likely will to forgo advertising in Washington state, Maine, Tennessee and Virginia.

Dean is raising $200,000 a day, enough to have mounted a sizable ad campaign in one or two states today, but aides said they stayed off the air out of extraordinary caution. They don’t want to run up a campaign debt that might be a personal burden to Dean after the race.

After balancing the books, aides predict they’ll have a large stash of money for an ad blitz in Wisconsin, site of a Feb. 17 primary.