Clark, a retired Army general, dropped out of the presidential race on Wednesday.
Clark spokesman Matt Bennett would not confirm the endorsement, but said, "General Clark is looking forward to going to Wisconsin to be with Senator Kerry" on Friday.
Kerry was taking a breather from campaigning Thursday after racking up 12 out of 14 caucus and primary wins, gearing up for a big Wisconsin push next Tuesday.
Meanwhile, his rivals were trying to craft last-minute strategies to derail Kerry from his winning streak and to pick up enough delegates for themselves to remain viable candidates.
Before Wisconsin's primary, the only state in play is Nevada, which holds caucuses Saturday.
Howard Dean (search), the former Vermont governor, is scrambling for ways to keep his struggling campaign alive. North Carolina Sen. John Edwards' (search) strategy, meanwhile, is to stifle a Dean comeback in Wisconsin, emerge as the obvious alternative and capitalize on being the sole Southerner left in the race.
"He's ahead and I'm the underdog," Edwards said of Kerry. "But I'm in the place that I wanted to be — one-on-one with somebody, in this case Senator Kerry."
While Kerry was taking another day off in Washington, D.C., Edwards was spending Thursday campaigning in Wisconsin before a trip to Los Angeles. Dean is campaigning in Wisconsin and Minneapolis, while Ohio Rep. Dennis Kucinich (search) will tape "The Tonight Show With Jay Leno" in Burbank, Calif.
Jobs, Jobs, Jobs
In Wisconsin, Edwards has been hammering home his message of jobs being lost overseas and the need for fair trade; 74,000 industrial jobs have been lost since Bush took office.
"We have to have a president who will fight for jobs," he said in Milwaukee. "People are desperate for someone who will protect their jobs and fight for jobs."
He also ripped the North American Free Trade Agreement (search), which Kerry voted for.
"If you look at my record in total, it's pretty clear what my position is on trade," said Edwards, who is airing ads in the state saying: "No one will do more than I will to keep American jobs right here in America."
Edwards said Thursday he'll keep his campaign positive but the big boost in support he expected with Clark out of the race may be blunted if his fellow Southerner endorses Kerry.
"The reason I broke through in Iowa in the last couple of weeks is because the positive message finally broke through," he said. "The same thing happened in South Carolina, where a couple of weeks before that I was behind. We surged ahead."
Edwards is mixing daily campaign events in Wisconsin with trips to other states like California. On Friday, he will stump in Milwaukee before heading back to California to raise money and appear on the "Tonight Show With Jay Leno."
Dean on Life Support?
Using a training mannequin that appeared lifeless before its chest heaved, Dean argued in Wisconsin that lobbyists, pharmaceutical companies and corporate health care have succeeded in blocking efforts to hold down costs and expand coverage.
"Special interests in Washington stop real change every time," he said. "The process is broken. In order to change America we have to change Washington."
Dean is busy crisscrossing Wisconsin with a mix of events, ranging from the town hall meeting of roughly 100 people in Oshkosh to his tour of a free clinic for the uninsured at the university.
The appearance of Dean's wife, Judy — who has remained out of the political spotlight but is now traveling with her husband — on the campaign trail may be one strategy Dean is employing to get his candidacy back on track. He also has developed a strategy that involves taking Kerry to task at every turn, usually without directly naming him, for his association with what Dean simply calls special interests.
A 'Super' Tuesday for Kerry?
The Alliance for Economic Justice (search) — an umbrella group of 21 international labor unions, including the Teamsters, United Auto Workers and United Steelworkers of America — which had previously endorsed Missouri Rep. Dick Gephardt, will officially announce their support on the eve of the Wisconsin primary.
Two of New York's most prominent black politicians, Rep. Charles Rangel and former state Comptroller H. Carl McCall, also endorsed Kerry.
The front-runner moved out to a commanding lead among likely voters for New York's March 2 primary, according to a poll released by The Quinnipiac University Polling Institute on Thursday.
The Massachusetts senator was favored by 53 percent of likely voters, including those leaning toward one candidate or another. Dean had 12 percent of the vote, Edwards had 8 percent; Al Sharpton had 4 percent and Kucinich had 3 percent.
Earlier independent polls conducted before Kerry's surge in the early primaries had shown Dean ahead in New York.
"It's beginning to look like 'Super Tuesday' March 2 ... will be super for Senator Kerry," said Maurice Carroll, director of the polling institute.
Edwards: 'I'm Definitely Staying In'
Edwards said he wouldn't drop out of the race, and not one Democratic official has asked him to.
"I'm going to be the nominee," Edwards said. "I'm definitely staying in."
Edwards has repeatedly been asked whether he would consider a vice presidential slot on a Kerry for president ticket but the boyish senator has steadfastly answered "no," saying reporters should be asking Kerry whether he would consider a No. 2 spot under Edwards.
Baldick said the campaign won't have enough money to advertise extensively in big Super Tuesday states but figures that Kerry's won't that, either. Edwards plans a tarmac-to-tarmac campaign to hold rallies where he hopes to grab the attention of as many local TV stations as possible.
In a television interview Thursday, Edwards said he's confident he can attract the independent and undecided voters that would be key for a Democratic win.
Edwards' team and polls suggest that the candidate knows he will lose Wisconsin, but is looking for a strong second-place showing. A blowout 15-25 point margin would end the race for Edwards, sources said.
The Kerry and Edwards campaigns are calling up Clark supporters, organizers and donors trying to get their support. Dean also thinks he will gain some Clark supporters because of the "fair amount of similarity in our outsider status," he said.
Meanwhile, in Milwaukee, Dean said Edwards is a better choice than Kerry for the nominee.
"I think Sen. Edwards would be a stronger candidate against George Bush than Senator Kerry because when Senator Kerry's record is examined by the public at a more leisurely time when we're not having primaries every week, he's going to turn out just like George Bush," Dean said in a television interview Wednesday night.
When asked about Dean's statement, Edwards said: "I agree with that very wise man."
"The truth is that this campaign to bring about change is working with independents and voters that we will have to get in order to win the general election, which is why I am the strongest candidate against George Bush," Edwards continued.
Fox News' Carl Cameron, Major Garrett, Catherine Loper and The Associated Press contributed to this report.