Born and raised in South Dakota, McGovern served as a B-24 pilot in World War II, and was awarded the Distinguished Flying Cross. (His wartime exploits were later at the center of Stephen Ambrose's book The Wild Blue.) On return from the war, he earned a PhD in history from Northwestern University and became a professor at his alma mater, Dakota Wesleyan University. After five years of teaching, McGovern quit to become more involved in South Dakota politics, which led to election to the House of Representatives in 1956.

After two terms in the House, he unsuccesfully ran for Senate in 1960, which made him available for appointment as the first director of President John F. Kennedy's Food for Peace program. In 1962, he stood for election to South Dakota's other Senate seat and won, serving his first of three Senate terms.

Although he voted in favor of the Gulf of Tonkin Resolution, McGovern later became a vocal opponent of U.S. military involvement in Vietnam, often criticizing the policies of fellow Democrat President Lyndon Johnson. At the 1968 Democratic National Convention, McGovern stood as the flagbearer for some of the supporters of the late Senator Robert F. Kennedy, losing the Presidential nomination to Hubert H. Humphrey, and coming in behind Minnesota Senator Eugene J. McCarthy as well. However, he and his supporters were able to win procedural concessions that eventually facilitated his successful nomination at the 1972 Convention.

In the 1972 election, McGovern ran on a platform of ending the Vietnam War and instituting guaranteed minimum incomes for the nation's poor. Between difficulties with his running-mate, Thomas Eagleton (who he eventually dropped and replaced with Sargent Shriver), and the Republicans' successful campaign to paint him as unacceptably radical, he suffered a 61% - 38% defeat to Richard Nixon- at the time the biggest landslide in American history.

After this loss, McGovern continued his involvement in politics, serving in the Senate until 1981, and even contesting the Democratic nomination for President in 1984. His importance in U.S. politics diminished over time, but his legacy endures as a symbol of the political left during the turbulent 1960s

He endorsed Democrat Wesley Clark's candidacy for the 2004 presidential election on January 18, 2004.