War hero, grassroots Democrat, US Representative, US Senator, unsuccessful Democratic Presidential candidate, and humanitarian.

McGovern grew up in Mitchell, SD (home of the famous Corn Palace). He enlisted in the Army Air Force days after Pearl Harbor, flew 35 missions over Europe, and was awarded the Air Medal and Distinguished Flying Cross. Returning home he joined the Democratic party in 1953 and literally re-built the South Dakota democratic party from scratch (when he joined the party it held no statewide offices and only 2 of the 110 seats in the state legislature). After being elected to the House and then the Senate, he became increasingly frustrated with the Vietnam war and finally ran for President, convinced that  was the only way to actually end the war.

It's important to note that republicans demonized him for decades after his unsuccessful Presidential run, not because he was wrong but because he was right. It's impossible to say how many American and Vietnamese lives he would have saved, as thanks in part to his opposition to the war the public had turned so much against it that congress terminated funding shortly thereafter. But the fact remains that he recognized Vietnam for the error it was starting in 1963, and with increasing volume and frequency starting in 1965.

Here's a quote from his speech on the Senate floor during the debate over the McGovern-Hatfield amendment that would have cut off funding for the Vietnam war:

Every Senator in this chamber is partly responsible for sending 50,000 young Americans to an early grave. This chamber reeks of blood. Every Senator here is partly responsible for that human wreckage at Walter Reed and Bethesda Naval and all across our land—young men without legs, or arms, or genitals, or faces or hopes. There are not very many of these blasted and broken boys who think this war is a glorious adventure. Do not talk to them about bugging out, or national honor or courage. It does not take any courage at all for a congressman, or a senator, or a president to wrap himself in the flag and say we are staying in Vietnam, because it is not our blood that is being shed. But we are responsible for those young men and their lives and their hopes. And if we do not end this damnable war those young men will some day curse us for our pitiful willingness to let the Executive carry the burden that the Constitution places on us.

With only a change of place, that speech could apply to every war fought since then. All fought for greed or to "send a message', none actually fought because of a military threat to the US.

I actually met the man once, he was the commencement speaker at my cousin's graduation from Catholic University in Washington DC. in 1974 I believe. I told him I wished he had been elected. He said that he wished he had too. After the disgrace of Nixon, I'd guess many Americans wished so as well.