What do Sen. Pete Wilson (R-Calif.), national security affairs adviser William P. Clark, former California governor Edmund G. (Jerry) Brown Jr., California Democratic Party Chairman Peter Kelly and about half of California's recent law school graduates have in common?

They all flunked the California state bar examination at least once. The legal profession's excruciating rite of passage has brought fear and controversy nearly everywhere, but the bar examination in this western mecca for young attorneys has the highest failure rate of any state in the union.

With the number of lawyers in history's most litigious nation soaring past the 600,000 mark, candidates for the bar are jamming into examination rooms in record numbers--an estimated 8,500 last week in California alone.

Of the 4,803 candidates who took the California bar exam in February, 27.7 percent passed, the lowest percentage in the country and a 60-year record low for California.

"It is cruel and unusual punishment," said Gregory Veal, 37, a city rent-control investigator trying for the fourth time to pass the exam.

"They are slowly but surely closing the door to more lawyers," said Elise Beraru, 29, trying again after failing in February. "Each year they make it harder and harder."

California bar officials and exam experts nationwide deny any significant changes in the difficulty or grading of their tests, but controversy over the fairness of the tests has revolutionized American bar exams in the last decade.

In the 1960s, prospective lawyers faced a patchwork quilt of state examinations, each with different sets and types of questions, each given at different times of the year. Now, on the same day, candidates in 46 states, plus the District of Columbia, Guam and the Virgin Islands, take a standardized multiple-choice law test for part of their score.

Noting complaints that the exam still measured only memory and not practical legal skill, California last week included in its essay portion of the test a "performance" examination. Each candidate received copies of cases, statutes and other material and was required to draft a series of mock memos to a senior law partner.

Such changes do not comfort the law student who has spent thousands of dollars in tuition, plus $750 for a bar review course and $250 in exam fees, and then fails the examination.

In California that problem is exacerbated by the relatively high 70 percent score required to pass the exam, and by its wide-open nature. Anyone who has graduated from law school, even if the school lacks state certification, can take the test.

Clark, who also served on the California Supreme Court, Brown and Kelly each failed the state bar examination once before passing the second time. Wilson passed on his fourth try. Wilson spokesman Otto Bos said the senator and former San Diego mayor had studied English literature at Yale and found that he was spending too much time crafting artful essays the first few times he took the exam. He passed when he switched to a typewriter.

Famous Californians who passed the first time include U.S. Attorney General William French Smith, Los Angeles Mayor Tom Bradley, San Diego Mayor Roger Hedgecock, Assembly Speaker Willie L. Brown Jr. and National Democratic Party Chairman Charles T. Manatt.

Richard Morris, special assistant to Clark and a veteran reappraiser for the California State Bar's committee of bar examiners, said the only reason so many fail the examination is because "anybody can take it."

He said Clark first took the examination in 1958 when he had a wife and three children and was working full time as an insurance claims adjuster in Ventura. He never completed college or law school, but had been studying on his own.

Jane Peterson Smith, examinations director for the committee of bar examiners, called California's system "a trade-off."

"In exchange for increasing the chances for failure, we extend to many more people the opportunity to pass, and that is the tradition of education in California," she said.

California bar officials said their February examination attracted large numbers of marginal candidates who had failed previous tests, and this helped produce the unusually low passing rate. But in the examination in July, 1982, only 47.5 percent passed. During the same week last year, the bar-exam passing rate in the District was 61.3 percent, in Maryland 65.2 percent and in Virginia 70 percent.

The D.C. Bar Examiners admit only graduates of ABA-accredited schools. Maryland and Virginia allow unaccredited law school candidates to take the test, but according to the National Conference of Bar Examiners the passing score for the standard multiple-choice part of the examination was 128 out of 200 questions in Virginia last year, compared with 140 out of 200 in California.

The multiple-choice test, called the Multistate Bar Examination, has been eagerly adopted by bar examiners since it was introduced in 1972. It offers a fixed standard that blunts complaints about subjective grading.

"The applicants themselves just hate it," said Joe E. Covington of Columbia, Mo., who is testing director for the National Conference of Bar Examiners. He spoke with the delight of a former professor who seems to enjoy seeing law students squirm.

"It makes them uncomfortable: they never know quite how well they did on multiple-choice questions," he said.

Cathleen Drury, 32, a law clerk, called the multiple-choice test "just terrible, just ridiculous" as she stood in a lobby of the Century Plaza Hotel here after a day-long struggle with the examination.

"You are trained as a lawyer to look at more than one side," she said. Bar examiners, however, point out that long experience with the Multistate Bar Examination shows that its scores compare closely with scores given the same students on essay questions.

Smith said her office ordinarily receives 300 to 1,000 complaints from unhappy exam takers after the scores come out. The pain of failure seems particularly unbearable to students who have devoted their few precious evening hours to law school courses designed to pull them into a higher-income profession.