Always a patriot, Mr. Cronkite supported the Vietnam War until the pivotal Tet offensive in 1968, when he donned a steel helmet and flak jacket to observe the situation for himself in Saigon and Hue. He returned to anchor a report, shocking at the time, whose conclusion still resonates decades later:

"We have been too often disappointed by the optimism of the American leaders, both in Vietnam and Washington, to have faith any longer in the silver linings they find in the darkest clouds. . . . For it seems now more certain than ever that the bloody experience of Vietnam is to end in a stalemate. . . .

"To say that we are closer to victory today is to believe, in the face of the evidence, the optimists who have been wrong in the past. . . . It is increasingly clear to this reporter that the only rational way out then will be to negotiate, not as victors, but as an honorable people who lived up to their pledge to defend democracy, and did the best they could."

In a famous reaction, President Lyndon B. Johnson told his aides, "If I've lost Walter Cronkite, I've lost middle America." Subsequently, he decided not to run for reelection.

David Halberstam, who won a Pulitzer Prize in 1964 while covering Vietnam for the New York Times, later wrote, "It was the first time in American history that a war had been declared over by a commentator."

Mr. Cronkite also influenced the Watergate scandal. Coverage, initiated by the Washington Post, was languishing nationally when Mr. Cronkite laid out the known facts in a lucid two-part report shortly before the 1972 presidential election.

"The White House went crazy, absolutely crazy," said CBS Evening News producer Sandy Socolow. Coverage perked up - "It was as if the story had been blessed by the Great White Father," said Washington Post executive editor Benjamin C. Bradlee - and remained unrelenting until Richard M. Nixon resigned the presidency in 1974. Mr. Cronkite was then at the peak of his popularity and influence. He had seized first place in the nightly news ratings in 1967 and never relinquished his grip.

"And that's the way it is," the closing line he made up, was said for the last time on the CBS Evening News on March 6, 1981. He was succeeded the following week by Dan Rather, who had worked with him for many years, notably as White House correspondent during Watergate.

CBS forced Mr. Cronkite out eight months before his normal retirement age, his 65th birthday, because it was anxious to retain Rather, who was being pursued by other networks. CBS locked Mr. Cronkite in what he called "golden handcuffs": He agreed not to work for either of the other major networks, NBC and ABC, and in exchange received a seat on the CBS board of directors and $1 million a year until he was 72.

Mr. Cronkite devoted much of his post-retirement life to promoting journalistic integrity and strengthening the craft through education.

At the request of Tom Chauncey, an old friend in Phoenix, Mr. Cronkite became involved in efforts to strengthen the journalism program at Arizona State University. In 1984, the university renamed its journalism department the Walter Cronkite School of Journalism and Mass Communication, giving the program "an immediate boost and national recognition," according to the school Web site.

Mr. Cronkite traveled to ASU each year to present the school's Walter Cronkite Award for Excellence in Journalism to a leading figure in the field.

In 1996, Paul Taylor, a former politics reporter at The Inquirer and the Washington Post, persuaded Mr. Cronkite to serve on the board of Taylor's Alliance for Better Campaigns. The goal of the alliance was to pressure television to improve its coverage of politics.

Mr. Cronkite "felt passionately that the broadcast industry had an obligation to keep people informed about elections and that they weren't doing a very good job of it," said Taylor, now executive vice president of the Pew Research Center in Washington. "He did not like the 30-second ad or the 8-second sound bite."

And Mr. Cronkite "was quite willing to use the moral authority he had gained as a broadcaster," Taylor said. "He used his halo to bash his former employers over the head."

Mr. Cronkite underwent heart bypass surgery in 1997, but he soon went back to work in cable TV, his haven after his long association with CBS ended.

In 1998, for CNN, he coanchored the coverage as former Mercury astronaut Sen. John Glenn returned to space at age 77 aboard the shuttle Discovery. In 1962, Mr. Cronkite had covered Glenn when he became the first American to orbit Earth.

To the end, Uncle Walter lived up to his description by the National Review: "A legend, a national father figure, a symbol of decency and good character."

He is survived by daughters Nancy and Kathleen, and his son, Walter Leland Cronkite 3d, called Chip.

This article contains information from the Associated Press.