Former Sen. George McGovern (S.D.), a mild-mannered champion of liberal causes and the 1972 Democratic nominee for president, died today after being moved into hospice care on Oct. 15. He was 90.

McGovern served two terms in the House and 18 years in the Senate. He built a legacy in Congress as a leading voice behind the national school lunch program and food stamps, and he is credited with establishing the Women, Infants and Children nutrition program.

But McGovern will always be best known for his presidential run against incumbent Richard Nixon in 1972. In that race, McGovern lost the popular vote 61 percent to 37 percent, at the time the second-largest landslide in modern times.

Later, as the Watergate scandal unfolded, news reports revealed that Nixon’s campaign had engaged in illegal activity as it attempted to sabotage the Democratic primary candidates.

The scandal, which came to light after a June 1972 break-in at the Democratic National Committee’s offices at the Watergate complex, eventually forced Nixon to resign in 1974. Some have argued that the break-in was intended to bring down Democratic nominee and frontrunner Edmund Muskie in order to set up a race against the more vulnerable McGovern.

McGovern’s campaign was plagued by problems after winning a bruising primary for the nomination. After his victory, Democratic opponents mockingly said his liberal platform stood for amnesty, abortion and acid. Shortened to triple A — as in “the triple-A candidate” — the moniker stuck throughout his campaign.

The tag stemmed from a column that appeared shortly after the 1972 Democratic convention by conservative writer Robert Novak, which included a quote from an unnamed Democratic Senator.

“The people don’t know McGovern is for amnesty, abortion and legalization of pot,” Novak quoted the anonymous Senator as saying. “Once middle America — Catholic middle America, in particular — finds this out, he’s dead.”

In a 2007 interview with NBC’s “Meet the Press,” Novak disclosed that the source of the quote was Sen. Thomas Eagleton (Mo.), whom McGovern had chosen to be his running mate. Eagleton had died in March 2007, freeing Novak from his journalistic obligation not to reveal a source.

“That was a secret that was kept until … his death, and … a lot of people said I had made up the name,” Novak said. “I had gone to Tom Eagleton and asked him if I could clear myself, since the campaign was long over, use his name. He said: ‘Oh, he had to run for re-election. The McGovernites would kill him if they knew he had said that.’ But it was Tom Eagleton.”

Eagleton was only on the McGovern ticket for just a few weeks. He withdrew after it emerged that he had received electroshock therapy for depression, causing some to raise questions about his ability to handle the job should he become president.

Longtime Democratic strategist Bob Shrum, who had worked on the McGovern campaign and appeared on “Meet the Press” with Novak, said: “Boy, do I wish he would have let you publish his name. Then he never would have been picked as vice president. … We had a messy convention, but he could have, I think in the end, carried eight or 10 states, remained politically viable. And Eagleton was one of the great train wrecks of all time.”

McGovern, a decorated World War II bomber pilot, was an outspoken and early opponent of the Vietnam War, a centerpiece of his presidential campaign.

However, at the behest of his colleagues, he voted for the Gulf of Tonkin Resolution, which gave President Lyndon Johnson a free hand in fighting the war. It was a vote he regretted.

“Well, I reluctantly supported that resolution because we were assured that two American destroyers operating on the high seas were attacked in an unprovoked — what was called an unprovoked attack by the North Vietnamese naval forces,” McGovern said in a 2005 Democracy Now radio interview. “Actually, we learned within a few months of the Gulf of Tonkin Resolution that there was no evidence that such an attack ever occurred. Even one of the commanders of one of the destroyers said at the time, … ‘Hold up, we are not really sure that there was any attack.’”

McGovern was later critical of Congress’ 2002 vote that essentially gave President George W. Bush the go-ahead for the 2003 invasion of Iraq.

“I couldn’t understand people with any historic memory at all voting to authorize war against Iraq in view of the way we had been so shamefully misled in the Gulf of Tonkin incident,” McGovern said in the same interview.

While in the Senate, McGovern championed programs for the poor, particularly battling hunger. He worked with Sen. Bob Dole (R-Kan.) — with whom McGovern was close — to establish WIC, food stamps and school lunch programs.

McGovern’s relationship with Dole prospered when he was selected to be chairman of the Nutrition and Human Needs Committee and Dole was chosen as ranking member.

In a 2011 C-SPAN interview, McGovern said he got the idea for the committee after watching a CBS News documentary called “Hunger in America” in 1967.

McGovern said he recalls telling his wife, Eleanor, “there are no hungry people in America; this is the richest country in the world.”

“I knew about hunger in the world — African, Asia, Latin America, parts of the Middle East … but I wasn’t really aware of the degree of hunger right here in this country,” McGovern said.

One scene that particularly bothered McGovern was when the reporter asked one child who was standing to the side in a school lunchroom how he felt about not eating. The boy responded that he felt ashamed because he didn’t have money for lunch.

“I remember saying to two of my daughters who were watching the program, ‘You know, it’s not that little guy who should be ashamed. It’s George McGovern, a United States Senator and I didn’t even know that students aren’t allowed to eat unless they had the money to pay for the lunch.”

McGovern said he went to the floor the next day and introduced a resolution creating the committee, and it passed without objection.

“From that day until we both left the Senate years later, [Dole] and I worked hand in glove on school lunches, on food stamps, on the WIC program, which we helped launch. … We revolutionized food assistance in this country,” McGovern said.

McGovern’s interest in nutrition stretches back to World War II, when the allies decided to distribute their remaining food before heading home.

“We were feeding our former enemies two days after bombing them,” McGovern said in an interview with New York Times food writer Mark Bittman last year. “It was an unprecedented gesture of good will.”