Former Senator George McGovern, who stood as the Democratic presidential candidate against Richard Nixon in 1972, has died, aged 90.

George McGovern was in a hospice in Sioux Falls, South Dakota, and slipped out of consciousness three days ago.

A liberal standard-bearer, George McGovern was a vocal opponent of the Vietnam War, but lost to Richard Nixon by a landslide.

He was first elected to Congress in 1956. During the World War II, he served as a US Air Force pilot.

“We are blessed to know that our father lived a long, successful and productive life advocating for the hungry, being a progressive voice for millions and fighting for peace,” said a statement released by his family.

George McGovern was admitted to hospice care earlier this month with a “combination of medical conditions, due to age, that have worsened over recent months”, his family said at the time.

His bid for the presidency in 1972 was marred by what later emerged as a dirty-tricks campaign by President Richard Nixon’s re-election committee, including the break-in at Democratic National Headquarters in the Watergate Hotel, in Washington DC.

Former Senator George McGovern, who stood as the Democratic presidential candidate against Richard Nixon in 1972, has died, aged 90

Richard Nixon, who already enjoyed an advantage throughout the campaign, won a second term in one of the biggest landslides in modern US history.

George McGovern had made two other brief attempts to obtain the Democratic nomination in 1968 and 1984.

At the time, he was seen as a leading voice of the Democratic party’s liberal wing.

After four years in the House of Representatives, he was one of the senators for South Dakota from 1963 to 1981.

George McGovern helped create the Food for Peace program, which sent US food overseas as a form of international aid, and became its first director in 1961.

Despite his failure to unseat Richard Nixon, he left an enduring mark on US politics: among his campaign workers in 1972 was a young Bill Clinton.

“I believe no other presidential candidate ever has had such an enduring impact in defeat,” Bill Clinton said in 2006 at the dedication of George McGovern’s library in Mitchell, South Dakota, according to the Associated Press.

“Senator, the fires you lit then still burn in countless hearts.”