Former senator Paul Laxalt (R-Nev.) and Robert B. Washington Jr., partners in the dissolving national law firm of Finley, Kumble, Wagner, Underberg, Manley, Myerson & Casey, yesterday announced the formation of a Washington-based firm they hope will avoid the bitter power struggles that brought down Finley Kumble.

The partnership of Laxalt, a longtime Republican Party activist with close ties to President Reagan, and Washington, a former head of the D.C. Democratic State Committee with equally strong connections to the city's top business and political leaders, is expected to be a major force in the legal community here.

"This is living proof of the Rainbow Coalition," Laxalt joked yesterday as he and Washington sat in Laxalt's office beneath photographs of Reagan and other GOP leaders.

With an upscale client list that includes Giant Foods, Northwest Airlines, Air France, the National Bank of Washington {NBW}, the CRS Sirrine Construction Co., the Tobacco Institute and the Washington Convention Center, the new firm will be bankrolled with a $15 million line of credit now being negotiated with NBW, the District's third largest bank, and three New York City financial giants, Manufacturers Hanover, Citibank and Bankers Trust.

Expected to open sometime next month, the firm -- Laxalt, Washington, Perito & Dubuc -- will have about 100 lawyers and maintain offices at its old Finley Kumble quarters on Connecticut Avenue and in the Willard Office Building. Finley Kumble's Washington office had 150 lawyers.

In addition, the firm will maintain an office in Baltimore and will work closely with a new firm to be headed by former senator Russell B. Long (D-La.) in Baton Rouge, La. Long, like Laxalt, had joined Finley Kumble less than a year ago.

Paul L. Perito will head the firm's special litigation practice, and Carroll E. Dubuc will be in charge of its aviation and product liability litigation.

Washington, who will serve as the managing partner of the firm, and Laxalt said the Washington partners have been talking of going it alone since Finley Kumble began unraveling in February.

After what Laxalt characterized as a particularly "ugly, acrimonious" meeting in September, he said it was apparent that "Finley Kumble was going over the cliff," and he credited Washington with helping to make the financial arrangements that kept the Washington office from going over the cliff, too.

As part of a complex financial deal to wipe clean Finley Kumble's $80 million debt to the four banks, the new Laxalt Washington firm will receive the $15 million line of credit.

However, the banks consider that about $10 million of that amount will cover the new firm's share of the predecessor firm's debt, leaving Laxalt Washington with $5 million in unused credit, according to a banker close to the deal.

"It's an innovative way for the new firm and the partners to remove the specter of their association with Finley Kumble and its debt," the banker said.

A lawyer and a banker close to the deal said that they believe the new law firm likely will merge with other law partnerships around the country in an attempt to create a national law firm.

At a meeting in New York Monday, Finley Kumble partners voted to set up a four-member "liquidating committee" that will use the firm's $130 million in assets to help pay off its debts.

Finley Kumble is expected to go out of business at the end of January.

Finley Kumble was launched in 1968 as a New York-based firm employing just eight lawyers. Its founding partner, Steven J. Kumble, had the then revolutionary notion of setting up a national law firm, one that would not have to refer clients to other firms for out-of-town legal matters.

Over the past decade, the firm merged with smaller firms, took on or "raided" additional high-profile and high-priced partners and soon grew into a far-flung operation with nearly 700 lawyers in 14 cities.

The firm's dismantling has its roots in the well-publicized power struggles of its name partners, especially Kumble; Marshall Manley, a former comanaging partner who built the firm's huge California practice, and Harvey D. Myerson, who replaced Manley as a comanaging partner and took over the New York office from Kumble about a year ago.

Washington, while declining to discuss the specifics of the firm's breakup, has said its difficulties were those of management and office politics, not bigness per se.

"After all is said and done, a law firm has to run on consensus and not just raising your hand and having the votes," Washington said.

Critics say Finley Kumble got into trouble because it overrewarded partners who were seen as good sales people and underrewarded partners and associates who were actually generating the firm's lifeblood, billed time. And the lawyers got a very good idea of how the rewards were being spread around because one legal publication printed the compensation paid to Finley Kumble's top 100 earners.

The article said top partners were expected to receive salaries this year that ranged from $800,000 for Laxalt and Long to $865,000 for Washington, $941,000 for Kumble, $1.2 million for Myerson and $1.5 million for Manley.

Washington called those figures "targets, goals" linked to expected profits, and he denied that any partner will make that much this year, especially now that the firm is disbanding. He declined to discuss salaries at the new firm, except to say, "We will do better than the average for law firms because we have the clients."