Labor rift a big test for unions in Mass.

Organized labor has long been a force to be reckoned with in Massachusetts. The biggest public construction projects of recent years, such as the Central Artery Project, have given preferences to union labor. On Beacon Hill, unions helped defeat a 2003 proposal by Governor Mitt Romney to scale back the state's generous unemployment insurance benefits.

And in the 2004 state election, unions helped Democrats expand their legislative majorities in the face of a highly visible and well-financed campaign by Romney to elect more Republicans.

But now, opponents are hoping this summer's split between the AFL-CIO and three major unions will weaken organized labor's influence on the state's economic and political affairs.

For example, Associated Builders and Contractors, which represents nonunion construction firms, said the split could prove a distraction for unions and help the builder's group end the union preferences in public construction.

''It's still an uphill battle," said Nathan Little, the construction group's public affairs director. ''But any time they have to spend organizing themselves is less time they have to spend at the State House."

Today, in Boston and across the state, Massachusetts unions will mark Labor Day with the national labor movement as fractured as its been in decades. This summer, the Service Employees International Union, Teamsters, and United Food and Commercial Workers, representing a total of 4.6 million members, broke from the AFL-CIO over the direction of the 50-year-old umbrella organization.

Under AFL-CIO president John Sweeney, organized labor has focused on politics, pouring money and manpower into supporting union-friendly candidates, albeit with mixed success.

In contrast, the breakaway unions, which formed a coalition dubbed Change to Win, wanted less money and effort spent on politics, and more on signing up new members.

A fourth union, Unite Here, which represents about 450,000 textile, hotel, and restaurant workers, is considering leaving the AFL-CIO.

Regardless of differences at the national level, state and local union officials say they will maintain the connections and unity of purpose that have made them a force in Massachusetts. Whether AFL-CIO or Change to Win, union leaders insisted they'll find ways to work together. They already have.

Since the national breakup, AFL-CIO unions have supported organizing drives by the Teamsters in Lynn and the Service Employees in Somerville. The Food and Commercial Workers recently joined the AFL-CIO affiliated Boston Teachers Union to urge parents not to shop for school supplies at nonunion Wal-Mart Stores Inc.

And with nearly 300 workers represented by the Service Employees preparing to strike at a Medford mental health center, the Massachusetts AFL-CIO has agreed to honor the picket lines.

''We all have the same mission: representing working people," said Robert Haynes, president of the state AFL-CIO. ''We plan to cooperate with these local unions. They didn't create this rift."

Gary Chaison, a professor of industrial relations at Clark University in Worcester, agreed that the national split is unlikely to divide local unions because their relationships are built not only on common interests, but also on long friendships.

''Local affiliates tend to be pragmatic," Chaison said. ''My sense is they will continue to cooperate and when it comes time to exercising power, they will come up with an organization or coalition to do it."

Still, local union officials conceded, the national breakup is making things more complicated. Traditionally, they have worked together under the umbrella of AFL-CIO-sanctioned labor councils, supported by dues paid by each of the member unions.

Most local leaders say they'd like to keep the labor councils intact, but the dispute at the national level is making that unlikely.

Change to Win leaders have instructed their unions to continue participating in and paying dues to local labor councils. The AFL-CIO, however, says these unions can remain in the labor councils only if they agree to conditions, such as paying a 10 percent surcharge on dues, which Change to Win has rejected.

Eventually, said Richard Brown, president of the Pioneer Valley Central Labor Council in Springfield, separate local councils might have to emerge: one for the AFL-CIO affiliates, one for Change to Win's.

Brown, meanwhile, might soon have to give up his labor council post because he is an officer of a United Food and Commercial Workers local.

''I would like to see this resolved so we're all under the same umbrella," Brown said. ''No matter what, we'll continue to work together, but I still think we need to have some collective voice."

Certainly, the last decade has not been particularly good for organized labor, nationally or in Massachusetts. Although the rate of union membership in Massachusetts remains slightly higher than in the United States -- 13.5 percent of workers vs. 12.5 percent -- it has nonetheless followed the national trend of steadily declining membership.

Today, Massachusetts unions represent 86,000 fewer workers than 15 years ago, according to the US Labor Department. In 1990, nearly 18 percent of Massachusetts workers belonged to unions.

The fracturing of the AFL-CIO could further reduce labor's impact in state politics, particularly Democratic politics, said Tim O'Brien, executive director of the Massachusetts Republican Party.

''In recent years, we've seen folks in unions start to vote Republican even though their leadership is strongly behind the other party," O'Brien said. ''So anything that weakens the leadership can only accelerate the process."

Local union leaders acknowledge that the division at the national level is encouraging perceptions like O'Brien's. But, they add, they are as determined as ever to maintain unity.

''We are committed to working together on issues of concern to working families," said Rich Rogers, executive secretary-treasurer of the Greater Boston Labor Council.

''Our goal is to minimize the conflict that has taken place in Washington, and to provide a model of local solidarity."

Robert Gavin can be reached at rgavin@globe.com.