In a straw vote, 23 board members supported Obama and 11 backed Edwards. Some said they preferred Edwards but voted for Obama to spite Clinton. They didn't explain their enmity for her.

Unite Here, which is by far the most powerful union in Nevada, announced its endorsement of Mr. Obama this afternoon. Unite Here's Nevada local, Culinary Local 226, represents more than 60,000 casino, hotel and restaurant workers, and is a power in local and state political races and is expected to be a powerful force in the January 19 caucuses.

With its announcement, Unite Here, which represents 460,000 hotel, restaurant, apparel and laundry workers nationwide, became the first national union to back Mr. Obama. Its leaders hope to help put him over the top in the Nevada and give his campaign new momentum.]

[Unite Here has been in a dispute with Senator Hillary Clinton's campaign because its pollster and chief strategist, Mark Penn, heads a public relation firm that has represented the Cintas Corporation, a large industrial laundry company that has vigorously battled the union's efforts to organize 17,000 Cintas workers.

Mr. Raynor said that dispute was just a small factor in why his union endorsed Mr. Obama.

"I gather Mark Penn is still involved in the campaign, which is very unfortunate," Mr. Raynor said. "Senator Clinton is a good person and a good friend, but we just disagree about Mark Penn."

Unite Here officials say their union will be a power in the South Carolina primary on January 19 because the union is one of the strongest in that state as a result of its long-time history in the apparel and textile industry. Unite Here is the successor union to the International Ladies' Garment Workers Union and the Amalgamated Clothing and Textile Workers Union. Mr. Raynor said Unite Here has nearly 6,000 active members and retirees in the state. .]