The labor unions that have invested millions in Howard Dean's (search) presidential bid are concerned that the beleaguered Democratic candidate is bracing for another round of losses that could put his campaign in peril.

The former Vermont governor plans to explain his strategy to stay in the race during a face-to-face meeting this week with the increasingly skeptical leaders of his three top labor backers -- the Service Employees International Union (search), the International Union of Painters and Allied Trades (search) and the American Federation of State, County and Municipal Employees. (search

SEIU President Andy Stern said his union, the largest in the AFL-CIO, is financially committed through the Wisconsin primary Feb. 17, but Dean needs to start winning primaries and caucuses if he's going to be the nominee.

"As Dr. Dean has said, he wants to win, he's not here as a protest candidate," Stern said. "At some point he's going to have to decide if he's getting enough delegates and does he have a strategy to win."

SEIU's political action committee has spent close to $1 million on polling, ads and get-out-the-vote efforts for Dean. An AFSCME PAC has spent more than $1.7 million.

Stern said the key to Dean's viability will be how John Kerry, winner of the Iowa and New Hampshire contests, does on Tuesday. Stern said if the Massachusetts senator wins all or most of the seven states, he could have the aura of invincibility, but losses to other candidates could make him vulnerable.

Dean came in a distant third in the Iowa caucuses last month, then saw his lead in the New Hampshire polls evaporate into a second-place finish. Dean has said he doesn't expect to win any of the seven states that vote on Tuesday, with the possible exception of New Mexico.

His strategy is to do well enough to win delegates in this weekend's contests in Michigan, Washington state and Maine while other candidates spend themselves out of the race. Then he hopes to become Kerry's last-standing rival in Wisconsin and beyond.

"Obviously people are nervous," said Bob Muehlenkamp, Dean's senior labor adviser. "Obviously they'd rather be in a different situation strategically. Obviously people have doubts and hesitations when you aren't winning elections and getting votes."

Dean adviser Gina Glantz said the campaign is trying to schedule the union meeting on Thursday or Friday, when Dean will be campaigning in Michigan. She said the leaders of the three unions also will spend some time on the stump in the strong labor state, which has 128 pledge delegates up for grabs.

Dean said Sunday that his labor backers have not reduced their support "as of this discussion."

"But," he added, "we will be meeting with them later in the week."

Stern said, "We're here solidly at the moment."

Doubts are not only rising among Dean's labor supporters, but morale is low at Dean's campaign headquarters in Burlington, Vt., aides say. Dean's staff had been working without pay since Jan. 28 to shore up campaign coffers after the New Hampshire loss, but the pay freeze was lifted on Monday and staff was told they will get the paychecks that were supposed to come last week.

Despite his campaign's fall from the front of the Democratic pack, Dean still has been raising about $200,000 a day from supporters on the Internet. He hopes he can continue to bring in enough money to keep him as the last man standing against Kerry later this month.