John W. Gardner, an eloquent voice for citizen participation who founded the Common Cause lobby, championed campaign finance reform and introduced Medicare as secretary of health, education and welfare in the heyday of President Lyndon B. Johnson's Great Society, died Saturday at his home on the campus of Stanford University in Palo Alto, Calif. He was 89.

Mr. Gardner died of complications from prostate cancer, which was diagnosed two years ago, his daughter Francesca Gardner said. Until recently, he had continued to speak and write as a self-styled American conscience, and died two days after the House of Representatives voted to approve a sweeping overhaul of the nation's campaign financing laws, a goal he had long sought.

In a career that spanned more than a half century, Mr. Gardner was a college teacher, a military intelligence officer, a philanthropic foundation executive, an author, a cabinet official, an adviser to presidents and, to many Americans, a personification of political reform and volunteerism in democratic society.

But he was perhaps best known as the founder of Common Cause in 1970. The organization spawned a grass-roots nonpartisan movement that opposed the Vietnam War, pressed the causes of civil rights and voter participation, campaigned to make national and state governments more accountable, and strengthened laws to require open meetings and full disclosure of lobbyists' gifts and favors.

As president of the Carnegie Corporation from 1955 to 1965, he helped shape the course of American education. He was chairman or a member of several presidential panels, including task forces on education during the Kennedy and Johnson administrations, President Jimmy Carter's Commission on an Agenda for the Eighties and President Ronald Reagan's Commission for Private Sector Initiative.

He helped established the Russian Research Center at Harvard and other Russian centers at Michigan and Princeton that became models for university research centers to study other parts of the world. He also persuaded Carnegie to sponsor a study that led to the new math, and is credited with generating a famous study by James B. Conant, the former Harvard president, that urged a return to basics in high school science, history, English and other subjects.

He came to President Johnson's notice as a presidential adviser during the Eisenhower and Kennedy administrations and as the editor of John F. Kennedy's book of speeches, "To Turn the Tide."

President Johnson was so impressed by the way Mr. Gardner handled the 1965 White House Conference on Education that he asked him to become secretary of health, education and welfare that year. Mr. Johnson also asked him to draw up plans for the White House Fellows Program to provide gifted young Americans with first-hand experience in government. Among the best- known graduates of the program are Secretary of State Colin L. Powell and the historian and author Doris Kearns Goodwin.

Mr. Gardner was the only Republican in the Johnson cabinet. The Democratic-dominated 89th Congress had passed no fewer than 189 major domestic laws, with many falling under Mr. Gardner's sprawling agency, which touched the lives of almost every American, from preschoolers to the elderly. With characteristic wit, Mr. Gardner described his mission as "a series of great opportunities disguised as insoluble problems."

With little explanation, Mr. Gardner resigned on March 1, 1968, after less than three years. The president and Mr. Gardner respected each other and shared an almost obsessive interest in education, but Washington insiders said there were strains between the two strong-minded men, and Mr. Gardner was too reserved and low key for the flamboyant circle of Johnson cronies.

Mr. Gardner told reporters that his departure did not arise from a specific disagreement. But the war in Vietnam was increasingly occupying the president, and the nation's domestic problems were relegated to a lower priority, as reflected in budget cuts.

There was much speculation about his next move. Would he become president of a university? Would he run for office? There was even talk of a race for president. Gov. Nelson A. Rockefeller of New York offered him the Senate seat from New York, which became vacant when Robert F. Kennedy was assassinated, but Mr. Gardner declined.

To his admirers, Mr. Gardner was a modern-day Plato, needed by Americans looking for optimism and idealism. But he had no taste for partisan politics, and, though only in his 50's, he thought he was too old. "It is too late," he said. "You have to have a certain temperament for politics, and I cannot develop it now."

James B. Reston, in a column in The New York Times, wrote that Mr. Gardner saw service to his country as a duty, "but a duty that can be performed from a university or foundation as well as from Washington," adding: "He will be in the battle, that is sure, but he will not be at the center of power, and that is a misfortune for the nation."

For a time after leaving his cabinet post, he headed the Urban Coalition, a group concerned about urban unrest, poverty and racial turmoil in the cities after the summer riots of 1967. Financed by businesses, the coalition lobbied for urban organizations whose voices were not being heard.

Mr. Gardner's time in Washington had convinced him that major problems could not be solved unless the political system was reformed from within. With the Democratic and Republican parties in mind, he told The New Yorker: "I think of people sitting in an ancient automobile by the side of the road. The tires are flat and the drive shaft is bent, but they're engaged in a great argument as to whether they should go to Phoenix or San Francisco. In my imagination, I am standing by the road saying, `You're not going anywhere till you fix the goddamn car.' "

His solution was to found Common Cause.

"Our political and governmental processes have grown so unresponsive, so ill-designed for contemporary purposes, that they waste the taxpayers' money, mangle good programs and smother every good man who gets into the system," he said. He said he wanted to rally alienated moderates worried that "their parties are in decay, their states aren't working right and their men in Washington aren't doing their job."

Common Cause, he said, would lobby not for special interests but for the people, seeking greater public participation in government and greater accountability by national and state officials. It would lobby for campaign finance changes, civil rights and higher ethical standards for public officials. It would stress the need for greater voter turnouts, and seek to restore public faith in government.

"Everyone is organized but the people," Mr. Gardner said as he began a huge direct mail and advertising campaign aimed at the "middle 80 percent" of Americans who were not liberals or conservatives, but "who want the system to work, who want to do something effective for their country."

There was some speculation that Mr. Gardner was using Common Cause as the basis for a third-party presidential campaign in 1972, but he denied it. And by 1974, Common Cause had 320,000 members and a $5 million budget. Despite critics who noted that its members were almost exclusively affluent and educated, Common Cause became part of the political scene, its positions often quoted with approval in the editorials of like-minded journals.

Over the years, it fought for many Congressional changes † challenging the stranglehold of the seniority system and seeking full disclosure of presidential and Congressional campaign contributions. It supported an 18-year-old voting age, opposed funds for the war in Vietnam and advocated greater oversight of defense spending and the influence of political-action committees.

If it never became the thunderous voice Mr. Gardner envisioned, Common Cause, which now has 200,000 members and a $10 million budget, remains a political presence and a testimony to its founders' outlook.

"When Americans attend open meetings or read their government's documents, or take part in our battered but resilient public finance system for presidential elections, there is a memorial to John Gardner," Scott Harshbarger, the president of Common Cause, said in a statement yesterday. "When we turn on public television, or when government insures no senior or poor person goes without health care, we take part in programs John Gardner initiated."

Patrician looks and a comfortable place in the establishment belied the modest origins of John William Gardner, who was born on Oct. 8, 1912, in Los Angeles, the younger of two sons of William Frederick Gardner, an Englishman, and Marie Flora Gardner. His parents, both real estate brokers, separated before he was born and his father died a year later. His mother raised her sons by selling houses in Beverly Hills, then a village surrounded by lima bean farms. She was a cosmopolitan intellectual and profoundly influenced his life.

He attended Stanford during the Depression and became a Pacific Coast freestyle swimming champion. For a time, he wanted to be a novelist and dropped out after his junior year to write fiction. After a year and half, he returned to the university, his manuscripts unfinished, convinced he needed to learn more about people. He received his bachelor's degree in psychology in 1935 and a master's degree a year later, and earned a doctorate in 1938 at the University of California.

He also met Aida Marroquin, a Guatemalan studying at Stanford, and they were married in 1934.

In addition to his wife and daughter Francesca, of San Francisco, he is survived by another daughter, Stephanie Trimble of San Francisco; a brother, Louis, of Carmel Valley, Calif.; four grandchildren; and two great-grandchildren.

In the late 1930's, Mr. Gardner taught psychology at the Connecticut College for women in New London and Mount Holyoke College in Massachusetts. He worked briefly for the Federal Communications Commission in 1942, then joined the Marine Corps. During World War II, he was assigned in Europe to the Office of Strategic Services, the forerunner of the Central Intelligence Agency, and left the service in 1946 as a captain.

After the war, he went to work for the Carnegie Corporation of New York, one of the nation's oldest private philanthropic foundations, whose grants to colleges and research and educational institutions helped shape educational policies in America.

Mr. Gardner became president of the corporation in 1955, and came to be regarded as one of the most powerful behind-the-scenes figures in education. His advice was sought † and often decisive † in picking university presidents, big-city school superintendents, even United States commissioners of education.

As chairman of a panel on education for the Rockefeller Brothers Fund, he coined the phrase "the pursuit of excellence," which was so widely embraced in education discussions at the time that it became a clichØ, much to his annoyance.

He was the recipient of many honors, including the 1964 Presidential Medal of Freedom, the nation's highest civilian award.

He was the author of many books, with titles like "Excellence," "Self- Renewal," "Morale" and "On Leadership," and he sometimes sounded like a preacher. Some critics called his books utopian and vague; even his friends thought he was a bit too moralizing. But many readers found his books inspirational. "Self-Renewal" was translated into eight languages.

In 1977, Mr. Gardner left the Common Cause leadership to found Independent Sector, an umbrella group of universities, museums, religious organizations and other private nonprofit institutions, with the idea of getting them to work together.

In 1989, he returned to Stanford as the Haas Centennial Professor of Public Service. Gardner Fellowships in public service, modeled after the White House Fellows Program, were established in his honor by Stanford and Berkeley. He was a trustee of Stanford, the Metropolitan Museum of Art, and many corporations, foundations and nonprofit organizations.