South Carolina Rep. Jim Clyburn (search) intends to endorse John Kerry (search), officials said Wednesday, a coup for the Democratic presidential front-runner the day after his win in New Hampshire.

The backing of the six-term Democratic congressman, the dominant black politician in his state, is critical in South Carolina, where almost half the voters in the Feb. 3 primary are expected to be minorities. Clyburn was courted by all of the Democratic presidential candidates.

"This is a significant sign of support throughout South Carolina for John Kerry and his plan to change America. Representative Clyburn is a leader in the African-American community," Kerry press secretary Stephanie Cutter said.

Clyburn, for his part, would neither confirm nor deny the impending endorsement.

His decision to side with Kerry was a particular blow to Sen. John Edwards (search), who has said South Carolina is a must-win state for him and whose campaign recently hired a former top aide to Clyburn who also had been working for Dick Gephardt (search). Clyburn had endorsed the Missouri congressman, who dropped out of the race after finishing fourth in the Iowa caucuses on Jan 19.

Edwards, campaigning in South Carolina, said he respected Clyburn, but added, "I think most of his supporters and his organization are with us."

Kerry campaign officials were scrambling to arrange a conference call later in the day with reporters traveling with the candidate.

Also Wednesday, Kerry was picking up the endorsement of Iowa Gov. Tom Vilsack (search), who had been neutral in the caucuses, although his wife, Christie, had endorsed Kerry and campaigned actively with him throughout the state.

Aides to Vilsack spoke on condition of anonymity about his plan to travel to Missouri later to make the endorsement. Expected to join him in endorsing Kerry were two former Missouri senators, Jean Carnahan (search) and Thomas Eagleton (search), Kerry campaign officials in Missouri said.

As he boarded a plane for St. Louis, Kerry said he was thrilled with the endorsements, and added, "I'm still going to make this a campaign about people. We have to build. We have to grow."

Carnahan said Kerry is the most electable of the Democrats because of his military background and national security policies.

"That's something most Americans are very concerned about," she said. "They want a strong defense, they want to feel safe here at home, they want to feel like we can make the kind of commitments abroad we need to keep the nation safe. They feel a lot more comfortable with someone who's had military experience, and certainly I do."

The endorsements showed that some in the party's establishment were moving in Kerry's direction. Eagleton was briefly George McGovern's running mate in the 1972 campaign, before he was dropped from the ticket amid the disclosure that he had been hospitalized three times for psychiatric treatment and twice treated for depression with electroshock therapy.

Kerry had pressed hard for an endorsement from Carnahan, the widow of former Gov. Mel Carnahan. In 2002, she lost her bid for a full-term in the Senate.

Kerry also had gained the backing of New Jersey Sen. Jon Corzine, head of the Democratic Senatorial Campaign Committee, on Tuesday.

Kerry campaign officials said the Massachusetts senator was close to gaining endorsements from the governors of Michigan and Arizona.

Kerry was moving aggressively to compete in the seven-state contest looming Feb. 3, where 269 delegates to the Democratic convention are at stake. That dwarfs the first two tests, offering 12 percent of the delegates needed to claim the nomination.

Kerry said he'll campaign in all seven of those states, including tiny North Dakota, and he's bought television ad time in all seven as well, including very expensive Missouri.

With 74 delegates and Gephardt now out of the race, Missouri is the biggest prize of all Feb. 3. Kerry also plans a heavy focus on South Carolina, but is likely to face competition from retired Gen. Wesley Clark for the veterans' vote.

In New Hampshire, surveys of those casting ballots showed Kerry's support was broad, roughly equal between women and men and among all age groups. Kerry got the strongest vote from those who described their views as moderate, not quite half the electorate. He got one-third of the vote from self-described liberals, and had roughly equal backing from independents and Democrats.

The exit polls were conducted for Fox News, The Associated Press and other media outlets by Edison Media Research and Mitofsky International.

About six in 10 voters who said experience was important voted for Kerry, and six in 10 who said the ability to beat President Bush was important went for Kerry. More than half of his supporters said they made up their mind in the last week.