Washington attorney Max M. Kampelman, the new U.S. arms negotiator, is a conservative Democrat and a tough bargainer who frequently has criticized the Soviet Union's human rights record.

In choosing Kampelman, a longtime associate of the late Democratic vice president and senator Hubert H. Humphrey, to head the team, Reagan passed over many of his senior advisers who would be considered more experienced on arms control issues.

But Kampelman is thoroughly grounded in the internal workings of Washington and is close to many of Reagan's closest advisers and supporters.

In a recent interview, Kampelman called himself a liberal on domestic affairs. On foreign policy, he said, "the Soviet philosophy is anathema to our values and a danger to national security. I also am, in many ways, a pacifist, and still want to avoid war. So negotiations are absolutely necessary.

"The ideal scenario would be that, as a result of our firmness and consistency and patience, the Soviets will come to understand that it is in their best interest to give up the Leninist ideas of world imperialism, of the brave new world which is theirs . . . . "

Kampelman was a conscientious objector during World War II. In lieu of military service, he worked at an institution for mentally handicapped children in Maine and for a University of Minnesota experiment on starvation. It was in Minnesota that he met Humphrey.

President Jimmy Carter gave Kampelman, 64, his first high-level negotiating assignment with Moscow, ambassador to the European Security Conference in Madrid. Reagan kept Kampelman in that post until it was ended in September 1983.

Kampelman had several clashes with the Soviets in Madrid. In January 1982 he criticized the internal exile of physicist Andrei Sakharov and said the Kremlin could not improve relations with the United States while it continued to "violate the rules of civilized behavior," including the Helsinki pact.

In July 1983, Kampelman told delegates to the 35-nation conference that the United States could not permit "a limited negotiating success . . . to make us forget . . . that signatures on a document do not necessarily produce compliance with its provisions."

Born in New York City Nov. 7, 1920, Kampelman was a legislative counsel to Humphrey from 1949 to 1955 when Humphrey was a senator from Minnesota. He once worked for the International Ladies Garment Workers Union.

He is a close associate of U.N. Ambassador Jeane J. Kirkpatrick, another conservative Democrat in the Reagan administration, who is scheduled to leave her post soon.

He was nominated by President Lyndon B. Johnson in 1967 to be the first chairman of the Washington City Council, but some congressional Republicans objected, charging that Kampelman, a director and general counsel of the D.C. National Bank, was involved in granting a $125,000 unsecured loan to Robert (Bobby) Baker, later convicted of tax evasion and larceny.

Kampelman withdrew from consideration, citing a conflict of interest between the City Council job and his law practice.Kampelman is a founder of the Committee for the Present Danger, formed in 1976 to call attention to what its members described as a growing and dangerous imbalance in military power between the Soviet Union and the United States.