A lawyer who clerked with William H. Rehnquist at the Supreme Court in the 1950s said yesterday that Rehnquist strongly defended the old separate-but-equal doctrine underpinning racial segregation in conversations among the clerks.

The former clerk, Donald Cronson, indicated that Rehnquist often argued that the doctrine, enunciated by the court in an 1896 case called Plessy v. Ferguson, was correct at luncheon meetings of the clerks in the days before the 1954 decision declaring it unconstitutional.

Cronson added, however, that "I think the whole issue is a silly issue." He said he regarded it as completely irrelevant to Rehnquist's qualifications, more than 30 years later, to become chief justice of the United States.

"All this was gone into ad nauseam when Justice Rehnquist was first confirmed in 1971 ," Cronson, now an international lawyer based in Switzerland, said in a telephone interview. "It's very much res judicata a matter already decided ."

Rehnquist is expected to win Senate confirmation as chief justice by a wide margin, but Democrats on the Senate Judiciary Committee reportedly plan to question him closely about his views on a wide range of issues, including his 1950s stand on desegregation, at hearings next week.

The debate over Rehnquist's views on racial matters dates to 1952-53, when he and Cronson were clerks for the late Supreme Court Justice Robert H. Jackson. The court at the time was discussing what to do about a series of cases involving segregation in the public schools.

Jackson's papers, now housed at the Library of Congress, show that he was perplexed about how to deal with the practice, torn between a belief that it was indefensible and a realization that it was "deeply imbedded in social custom in a large part of this country."

At one point, Cronson turned in a memo stating that "there is no doubt that Plessy was wrong," and suggesting that the court say so. The memo, entitled "A Few Expressed Prejudices on the Segregation Cases," suggested that the court try to "straighten out the mess" by repudiating the separate-but-equal doctrine and inviting Congress to fashion the remedies.

Rehnquist countered with a memo over his initials, entitled "A Random Thought on the Segregation Cases," and contending that any attempt to strike down the practice would be wrong-headed and futile.

"I realize that it is an unpopular and unhumanitarian position, for which I have been excoriated by 'liberal' colleagues, but I think Plessy v. Ferguson was right and should be reaffirmed," the memo stated.

The document came to light in 1971 during Senate floor debate, after Rehnquist's confirmation hearings had been concluded, and he was never questioned about it. But he blunted the criticism with a letter in which he stated that he had prepared the memo at Jackson's request and that it was intended as "a statement of his Jackson's views" at an upcoming conference of the justices "rather than as a statement of my views."

Cronson, then with Mobil Oil in London, followed up with a cable affirming that Jackson had requested the second memo "supporting the proposition that Plessy was correctly decided." Cronson added that he and Rehnquist both worked on it.

In the telephone interview yesterday, however, when asked who the "I" was in "I think Plessy v. Ferguson was right," Cronson emphasized that he didn't write the entire memo and reiterated that "I thought it was wrong."

As for Rehnquist, Cronson said, "unquestionably, in our luncheon meetings with the clerks, he did defend the view that Plessy was right. Bill Rehnquist has never been afraid to defend an unpopular position. The very fact that it was unpopular would be an incentive for him to argue it . . . . But he defended all kinds of outrageous things, which I know he didn't believe."

Asked what Rehnquist believed on this particular issue, Cronson declined to say. "I have a view as to that he thought," he said, "but I don't think it's material."