On Tuesday, Deputy Solicitor General Lawrence G. Wallace will don a dark gray morning coat with tails, gray striped pants and his lucky black-and-silver striped tie. He will have mentally rehearsed his arguments -- while shaving, over breakfast and on the drive to work.

Many lawyers readying themselves for the singular experience of arguing before the Supreme Court do a "moot court" practice round with pretend justices. But Wallace won't, because "I want to reach my peak" on Tuesday.

Then in the hushed atmosphere of the white-marble courtroom, when Wallace begins defending the federal government in a dispute over truck regulations, he will make history.

In arguing his 127th case before the justices, Wallace will tie the record for the most cases argued by a living Supreme Court advocate. It is held by Erwin N. Griswold, a former solicitor general and former dean of the Harvard law school.

Wallace, who usually argues about four cases a year and has no immediate plans to retire, will probably surpass Griswold this term.

"I've worked here under seven presidents. The first one was named Johnson," Wallace says, and with a deliberate pause adds, "Lyndon rather than Andrew."

Wallace handles many of the government's meat-and-potatoes cases -- tough regulatory disputes that can mean a difference in how agencies operate. Administrative law, antitrust and taxes are his fields. While such cases lack the profile of constitutional controversies over abortion and the death penalty, they come to the court in greater number and require a lawyer to dig deep into the statute books and record of lawmaking.

"I never even consider going before the Supreme Court and arguing a case without talking to Larry Wallace first," said Solicitor General Drew S. Days III, who heads the elite group of lawyers responsible for representing the government before the nation's highest court.

A self-described anachronism, the mustachioed Wallace is exceedingly formal when he stands at the lectern before the justices. Days said Wallace's advantage is that he gets to the heart of an argument quickly. "He has a very good feel for how to present a case in a crisp and direct way," Days said.

Wallace, who has been arguing longer than any of the current justices has been sitting on the court, can be a bit impatient. He holds fast to where he wants the arguments to go, rather than where the justices may try to route him.

During an October oral argument, when one justice presented a hypothetical scenario that undermined Wallace's claim, Wallace admonished in his rasping voice, "Quite so, your honor, but we're getting afield from what happened in this case and what this case was about."

Paul Bender, a special deputy solicitor to Days, called Wallace "the quintessential government lawyer. He has very high standards for the office. Everything has to be done the right way."

But Wallace has a quirky streak. He refused to give his age -- it's 63 -- and until recently wore an ill-fitting black serge morning coat that he bought secondhand for $13.

"Although I am generally a keeper of the tradition of the office," he said in an interview earlier in the month, "I wouldn't mind dispensing with the morning coat... . It has shrunk over the years." Wallace laughed at his own quip, acknowledging that he doesn't cut the figure he did 25 years ago.

Yesterday he told a reporter that "after 126 arguments" in the black serge, he was retiring it for the new gray coat. During his October argument, it was apparent that a seam had given way on his old favorite.

Days, a former assistant attorney general who has known Wallace since the 1970s, was aware when he took over the solicitor's office in early 1993 that Wallace had racked up a big record of oral arguments.

"Shortly after I became solicitor general, I thought I would have a little fun with Larry," Days recalled recently. "He had about 123 arguments then, and I said, 'Larry, there are a lot of things on my mind, I think there is one thing you can help me out with... . I don't know whether to play you regular rotation or out of line,' " so Wallace could argue more cases than the other lawyers in the office.

"And Larry said, 'Regular rotation.' " But Days added with a laugh, "He hesitated."

Wallace's colleagues say his high number of court appearances has been a source of both drive and pride. According to court records, only one lawyer in this century presented more arguments than Wallace and Griswold: John W. Davis, who was solicitor general from 1913 to 1918, with 140 cases.

"Nothing that I or anyone else will do will diminish the career that Erwin Griswold has had," Wallace said of the distinguished Griswold, 90, who was appointed solicitor general by Lyndon B. Johnson in 1967 and was retained until 1973 by Richard M. Nixon.

Wallace has remained captivated by the assignment that most lawyers would die for. "I still get stimulated" before an argument, he said. "But I don't get panicky." Born in Syracuse, N.Y., the youngest of three children, Wallace was the first in his family to become a lawyer.

The case he will argue Tuesday, Interstate Commerce Commission v. Transcon Lines, will test enforcement of the federal "filed rate doctrine," under which interstate trucking companies must publish and stick to their shipping rates.

The solicitor general and his assistants defend a particular position before the justices, just as private lawyers do. But they have an additional responsibility to look beyond their own interests. Sometimes called the "10th justice" or "handmaiden" to the court, the solicitor general is relied on for an unbiased presentation of the facts of a case and often called upon to advise the justices in disputes in which the government is not a party.

Wallace said the government's bottom line in a case "is not as important as the integrity of the process, the candor of our presentation. We want to make sure the court is fully informed about everything that goes on in the case."

Yet, from any advocate's point of view, the purpose of oral arguments is to persuade the justices.

"Do we sometimes count votes going in?" Wallace asked rhetorically. "To some extent we can anticipate. But the justices are by and large open-minded. One of the worst things an individual advocate can do is try to maneuver around the justices. That can be transparent. It is not an occasion for tricks."

Wallace came to the solicitor general's office in a Democratic administration and rose in ranks during GOP and subsequent Democratic eras.

"I have relatively little discomfort" with changes in administration "as long as I feel we are not concealing anything from the justices," he said. "We have an institutional role to defend acts of Congress and the way agencies are administering policy."

One of the tributes that Wallace values most is a July 2, 1987, letter from retired Justice Lewis F. Powell Jr., which Wallace has framed and hung on his office wall.

Powell, who had just announced he was stepping down, wrote, "As you will understand better than most, I will miss the court. I also will miss your arguments. They rank among the very best the court hears. The government is fortunate to have an advocate of your quality."

Wallace is also an accomplished violinist who "has performed in just about every hall in Washington." During an interview, he enthusiastically produced, "as Exhibit A," three compact discs of classical music in which he had been in the performing orchestra.

Wallace reveals some of his performing side when he stands before the justices and speaks with a tone of superiority for the full federal government.

Said Wallace, "I don't really think of having a style... . I sometimes say, 'You wind me up and I argue.' "

LAWRENCE G. WALLACE

deputy solicitor general

EDUCATION

BA, Syracuse University, 1952, MA, 1954; Columbia Law School, 1959.

CAREER HIGHLIGHTS

Law clerk, Justice Hugo Black, 1960-61; professor of law, Duke University Law School, 1961-68; Solicitor's General Office, Justice Department, 1968-present.

PERSONAL

Single; professional violinist, played at opening of Kennedy Center during performance of Leonard Bernstein's "Mass."