Already facing upheaval and dissent from several union presidents, the A.F.L.-C.I.O. saw its problems escalate last week when the federation laid off about a fourth of its staff and the chairman of its public relations committee resigned in a fit of pique. Not only that, but four of the nation's largest unions demanded that the A.F.L.-C.I.O. remove their members' names from its master political list of 13 million workers because of a feud over sharing information.

Adding to the discord, the presidents of five unions - the service employees; the Teamsters; the laborers; the food and commercial workers; and the hotel, restaurant and apparel workers - plan to gather in Las Vegas on Monday to discuss whether to back a challenger to John J. Sweeney, the A.F.L.-C.I.O.'s president, in his bid for a new four-year term.

The A.F.L.-C.I.O., a federation of 57 unions, has been in tumult for more than six months, ever since the federation's largest union, the Service Employees International Union, threatened to quit, complaining that the organization was doing far too little to reverse labor's decline.

Andrew Stern, president of the service employees, which has 1.8 million members, has urged the federation to spend far more on unionizing workers. He has contended that much more organizing is needed because unions have lost clout as the percentage of workers in unions has fallen to 12.5 percent from nearly 35 percent in the 1950's.

The layoffs of 105 of the federation's 450 workers stem partly from Mr. Stern's call to have the federation concentrate more and spend more on unionizing millions more workers. The layoffs will help free $15 million to give to individual unions to help with organizing.

In revamping the A.F.L.-C.I.O., which was running a budget deficit, Mr. Sweeney eliminated the international affairs department, merged the political and field mobilization departments, and combined the legislative, policy and occupational safety departments. He also eliminated the monthly magazine, America@work, which was distributed to 160,000 union leaders and activists.

"There will be some things we can't do anymore or won't do anymore," said Denise Mitchell, the A.F.L.-C.I.O.'s communications director.

Mr. Sweeney announced the major changes on April 28. The next day, Harold Schaitberger, the general president of the International Association of Fire Fighters, sent a scathing letter saying he was resigning from the chairmanship of the federation's public affairs committee, complaining that Mr. Sweeney had failed to tell him about such an important announcement.

Mr. Sweeney has raised the federation's outlays on union organizing to $22.5 million, a $10 million increase. Mr. Stern and his allies had called for the federation to spend $65 million a year on organizing, and several of them complained that Mr. Sweeney's changes did not go far enough.

"There's a chasm between what Sweeney proposed on organizing and what we've been pushing for," said John W. Wilhelm, president of the hospitality division of Unite Here, which represents hotel, restaurant and apparel workers. "What Sweeney is doing is rhetoric, not substance."

The five union presidents who intend to meet in Las Vegas plan to discuss strategies to revive organized labor, and having Mr. Wilhelm run against Mr. Sweeney is one move they are considering.

Several Wilhelm allies said that he would like to run, but that a big obstacle is that his support, at least for now, appears limited to unions representing less than 40 percent of the federation's membership. The vote will take place in July at a convention in Chicago. Mr. Sweeney has said he has the race locked up, claiming support from unions with more than half the membership.

Another factor likely to affect Mr. Wilhelm's decision to run is whether the service employees leave the federation, a move that would greatly weaken his support.

The fight over the computerized political lists has aggravated the tensions. Thanks to those lists, organized labor's get-out-the-vote operation has been one of the Democrats' biggest assets. Officials from the Teamsters and several other unions complained that the A.F.L.-C.I.O. had not shared with them information it had gathered to help its political efforts, like whether union members in certain states had gun licenses.

"Deleting those records from our files would cause us to lose a lot of important data," said Ms. Mitchell, the federation's spokeswoman, "and that could hurt the political efforts of the whole labor movement."