Union rebel Andrew L. Stern has mounted an insurrection that could invigorate and transform the ranks of low-paid, heavily minority and immigrant workers in service industries across the country. Or it could destroy the house of labor.

The maverick who heads the Service Employees International Union has justified his decision to fracture the union movement by arguing that organized labor, under the direction of longtime AFL-CIO President John J. Sweeney, is in a downward spiral. The consequences, he said, are workers with diminishing paychecks and disappearing health care.

Stern, 54, effectively gambled the future of the labor movement Monday when he yanked his 1.8 million members and $10 million in annual dues out of the AFL-CIO. His move inspired others to take flight, including the International Brotherhood of Teamsters and the United Food and Commercial Workers, both with a total of 2.6 million members and about $18 million in annual AFL-CIO dues.

Stern began his insurgency two years ago. His vision was that the demands of a rapidly changing global economy require a consolidation by labor. By this reckoning, the loose affiliation of unions, many of them small, that characterize the AFL-CIO is no match for well-financed international corporations. Stern believes that unions must be forced to merge to create larger units that can dominate economic sectors, and that labor must shift more of its union dues into large-scale organizing campaigns and less distributing money to influence political races.

If his ideas prevail, Stern boasted, "the next decade can be a time of innovation, new strategies, new energy, new growth, and new ideas that will bring to life a new, 21st century American Dream."

Sweeney, 71, who used to be Stern's mentor, instead sees a nightmare in this week's events: "Employers are gloating over the fact that major unions have disaffiliated and that there is a split in the labor movement."

After his failure either to force Sweeney to retire or to gain AFL-CIO approval for his far-reaching reform proposals, Stern seized a dominant position in the newly formed Change to Win Coalition, an alliance of seven unions, most of them defectors from the AFL-CIO.

Of all the unions involved in the coalition, Stern's SEIU is widely viewed as the best equipped for the ruthless competition in organizing and membership raids that has already begun between the AFL-CIO and the coalition's unions.

During his 10 years as president of SEIU, Stern has built a team of organizers and strategists that aims to be the vanguard of a new union movement. They call themselves "The Purple Blitz," named after the color that is SEIU's signature. These organizers have added hundreds of thousands of new members to SEIU, cracking such tough-to-organize industries as building janitorial and cleaning services. In the process, SEIU became the largest union in the AFL-CIO.

Well before SEIU formally severed its ties to the AFL-CIO, it had already begun defying AFL-CIO rulings granting other unions -- especially SEIU's main competitor, the American Federation of State, County and Municipal Employees -- organizing rights over key blocks of workers, especially home health-care workers, a growing sector and a prime labor target. As SEIU's aggressive strategies broke new ground, Stern's contempt for what he sees as the tradition-bound leadership of Sweeney and of others, especially in the hard-hit manufacturing sector, grew more open.

But his bold gambit to strike out on a new path is risky. There are two basic questions, according to veteran labor observers. The first and most immediate involves the strength of Stern's allies.

Even though SEIU is primed for the fight, there are widespread doubts about the ability of Stern's top allies, the Teamsters and the United Food and Commercial Workers, to compete effectively in the battle that is taking shape in the aftermath of the split.

These two unions have only recently begun to build organizing machinery, and they will now be without the extensive support provided by the AFL-CIO -- support that had been crucial to recent Teamster victories. Instead, the two unions are now likely to face tough competition and opposition from unions that have stayed within the AFL-CIO.

The other -- and ultimately more important -- question is the relevance of the labor movement.

In the United States, intensified union organizing has been unable to compensate for the net loss of union members. Before last week's schism, the member unions of the AFL-CIO had already tripled their rate of organizing new members, from an estimated 150,000 a year in the 1980s and early 1990s before Sweeney took office, to 448,000 a year, after he became president. But even with this faster growth, overall union membership has continued to drop, from 14.5 percent of the workforce in 1995 to 12.5 percent last year.

Much of this decline has been the result of a rapid acceleration in the rate of U.S. manufacturing job losses. A total of 2.8 million manufacturing jobs were eliminated during Sweeney's 10 years in office, substantially more than the 2.2 million during the previous 15 years, from 1979, when the highest level of manufacturing jobs was reached in this country, to 1994.

Stern and his allies now propose that unions in the United States should view the 87 percent of the workforce not represented by unions -- particularly those concentrated in the fast-growing service sector -- as a vast opportunity for growth. He and his allies cite as prime targets for organizing those workers whose jobs cannot be moved overseas, or shifted from state to state to defeat union mobilization efforts: hospital and home health-care workers, hotel and casino employees, waste haulers and public employees.

Those workers whose jobs cannot be shipped are the prime targets of the unions that have defected from the AFL-CIO or are considering doing so. These workers are, in addition, already the targets of the organizing efforts of a host of other unions, many of them declining craft and manufacturing unions that are struggling to replace the disappearing membership in their core industries, such as steelworkers, longshoremen and machinists.

Andrew L. Stern of the Service Employees International Union explains the decision he and Teamsters chief James P. Hoffa made to leave the AFL-CIO.