All seven Democratic candidates are expected to take part in the 90-minute debate, scheduled for 7 p.m. ET at the Peace Center for the Performing Arts in Greenville, S.C.
The debate comes as former Vermont Gov. Howard Dean's campaign tried to rebound from back-to-back losses to Sen. John Kerry in Iowa and New Hampshire.
On Wednesday, Dean ousted Joe Trippi, his popular campaign manager, and suspended paychecks for his staff for two weeks to cope with a serious cash shortage.
Trippi is being replaced by Roy Neel, a veteran aide of Vice President Al Gore. The paycheck suspension signaled Dean's financial problems. He spent heavily on TV advertising in Iowa and New Hampshire, but he is now the only candidate who is not on the air in at least one of the seven states holding primary elections or caucuses.
"I think you are going to see a leaner, meaner organization," Dean said. "We had geared up for what we thought would be a front-runner's campaign. It's not going to be a front-runner's campaign. It's going to be a long, long war of attrition."
It was a stunning turnaround for the former front-runner, who seemed unstoppable only months ago, when he rode high in the polls and easily outpaced his rivals in campaign contributions.
Now Dean badly needs a primary victory to maintain a credible candidacy.
"Success in the next 10 days is absolutely essential," said Dean's campaign chairman, Steve Grossman.
Kerry, meanwhile, collected a key endorsement from Rep. Jim Clyburn, the top black Democrat in South Carolina, a state where African Americans make up about 30 percent of the population.
Clyburn said Kerry offers the best hope for a state that has suffered job loss with the decline in the textile and tobacco industries.
"When you look at the future, who has the resume, who has the experience to bring our country back together again?" Clyburn asked. "My choice is John Kerry."
Kerry had competed hard with North Carolina Sen. John Edwards, a native of South Carolina, for Clyburn's backing. The congressman had endorsed Rep. Dick Gephardt before the Missouri Democrat dropped out of the race.
Edwards has labeled the South Carolina primary win-or-else for his candidacy. Wesley Clark and Sen. Joe Lieberman have hopes for improved showings, while Rep. Dennis Kucinich and Al Sharpton also rated places on the debate stage.
In all, 269 delegates will be at stake on Tuesday in primaries in Missouri, Arizona, Delaware, Oklahoma and South Carolina, plus caucuses in North Dakota and New Mexico. Michigan and Washington state hold caucuses four days later.
The Democrats made campaign rounds while President Bush traveled to New Hampshire, where he hoped to counter the impressions left by weeks of anti-administration rhetoric.
In a sign of his new front-runner status, Kerry came under fresh attack from the Republican leadership, as RNC chairman Ed Gillespie again criticized Kerry's record on defense.
Gillespie acknowledged the Massachusetts senator's service in Vietnam – President Bush was in the Texas Air National Guard – but said Kerry's record was one of "advocating policies that would weaken our national security."
The RNC chair said Kerry backed a nuclear freeze in 1984, opposed the first Persian Gulf War in 1991 and proposed cutbacks in the armed forces in 1993.
In rebuttal, Kerry told reporters he was eager for a debate over defense issues, adding, "That is precisely the strength I bring to the race."
He said he has a long record of not only backing defense spending, but voting for smarter spending programs.
Former President Clinton, asked by reporters Thursday if Kerry is too liberal to be elected, said he thought it wasn't fair to describe Kerry as too far to the left or unelectable.
"He was good on security, good on fiscal responsibility, good on welfare reform. And I still think we've got a good field," Mr. Clinton said while visiting Washington to meet with Senate Democrats.
"I like all these people. I admire them. They've made a contribution to whatever good I was able to do for the American people, and I'm not going to get involved in it."