On Election Day, Mr. McGovern carried only the District of Columbia and Massachusetts, which added to political folklore the bumper stickers, “Massachusetts: The One and Only,’’ and “Don’t Blame Me, I’m from Massachusetts.”

“Just the assurance that one big, important state preferred me to go to the White House over the incumbent president meant a lot to me,” Mr. McGovern said in a 2004 Boston Globe interview. “I have genuine affection for Boston and Massachusetts.”

Mr. McGovern’s nomination marked a crucial turning point for the Democratic Party, which in just eight years went from Lyndon B. Johnson’s landslide victory of 1964 to Mr. McGovern’s landslide defeat. The sharp leftward swing represented by Mr. McGovern’s nomination created enduring scars.

Employed by Democrats as well as Republicans, the terms “McGovernite” and “McGovern wing of the party” lived on in common, and derogatory, use long after Mr. McGovern was defeated for reelection to the Senate in 1980.

He lost his seat in the Reagan landslide of that year.

The GOP victory could be seen as climaxing the transformation of the Republican Party that began with Barry Goldwater’s loss to Johnson in 1964. Unlike 1964, which also saw a highly divisive triumph of one wing of the party over its mainstream, 1972 was an end rather than a beginning: the death knell of the famed FDR coalition, which had dominated US politics for 40 years and given the Democrats control of the White House for all but 12 of those years.

Mr. McGovern’s fervent opposition to US involvement in Indochina and the general perception of his radicalness—best encapsulated, however inaccurately, as “acid, amnesty, and abortion,” a harshly reductive summary coined by then-Senate minority leader Hugh Scott—thoroughly alienated three already wavering mainstays of the coalition: the South, labor, and white ethnics.

Yet Mr. McGovern’s leftism is easily exaggerated. The most popular Democrat of the past 40 years, President Bill Clinton, helped run the McGovern presidential campaign in Texas. And Mr. McGovern’s nomination could be seen as affirming an even longer-standing Democratic tradition than that of the FDR coalition: Midwestern progressives heading the ticket. William Jennings Bryan, Adlai Stevenson, Hubert Humphrey, and, later, Walter Mondale shared with Mr. McGovern heartland roots, unabashed liberalism, and a poor showing in the Electoral College. The most recent exemplar of that tradition, Barack Obama, met with more success.

In his 1977 autobiography, “Grassroots,” Mr. McGovern recalled that it was Stevenson, “my first genuine political hero,’’ who inspired him in 1952 to become more than a merely nominal Democrat. He had considered himself a strong progressive before that but had remained true to the Midwestern tradition of nonpartisanship and “voting the man.” It was one of the few legacies of the Great Plains he abandoned. From his flattened vowels to his high moral tone, Mr. McGovern remained very much a product of what the poet Hart Crane once called “the prairies’ dreaming sod.”

As the son of a Methodist minister, George Stanley McGovern came by that moral tone naturally. He was born on July 19, 1922, in Avon, S.D., a community of about 600 people. His parents were Joseph C. McGovern and Frances (McLean) McGovern. He excelled as a high school debater, despite what he later described as his “inhibited style of speech delivery,’’ and entered Dakota Wesleyan University, in Mitchell, S.D., to which the McGoverns had moved a few years after their son’s birth.

Mr. McGovern interrupted his studies to enlist in the Army Air Corps during World War II. Prior to shipping overseas, he married Eleanor Stegeberg, who had been a fellow student at Dakota Wesleyan, in 1943. He served as a B-24 pilot in Europe, flying 35 combat missions and receiving the Distinguished Flying Cross and an Air Medal with three oak leaf clusters.