WASHINGTON : Former US senator Thomas Eagleton, who was dropped as George McGovern's presidential running mate in 1972 after he admitted having undergone shock treatment for depression, died Sunday at age 77, his family said.

Eagleton, in declining health for several years, died at St. Mary's Health Center in Richmond Heights, Missouri, the state he presented in the US Senate for 18 years until 1986, his family said in a statement through the law firm Thompson Coburn LLP.

"The cause of death was a combination of heart, respiratory and other problems that overwhelmed his weakened system," the statement said.

Democratic presidential candidate George McGovern picked him as his running mate for the 1972 election against Richard M. Nixon, with the Democrats campaigning strongly on an anti-Vietnam war platform.

But Eagleton was forced to step down after it was disclosed that he had undergone psychiatric shock treatments for depression during the 1960s.

Just days after saying he supported Eagleton "1,000 percent," McGovern replaced him with Sargent Shriver. The shift was thought to show McGovern as weak, and to contribute eventually to the Democrats being routed by Nixon's Republican ticket.

Born in St. Louis, Missouri, on Sept. 4, 1929, Eagleton had an early passion for politics.

"The way other kids wanted to be farmers or firemen or cowboys, I wanted to be a politician," he once said.

After graduating from Harvard Law School, he took a job as assistant general counsel to US beer maker Anheuser-Busch.

Eagleton then became the youngest candidate to be elected St. Louis circuit attorney at age 27, before becoming Missouri's youngest attorney general at 31 and the state's youngest lieutenant governor at 35.

He won a Senate seat in 1968 and became known as an outspoken Vietnam war opponent.

In 1973 he successfully offered an amendment to a defence appropriations bill to cut off funding for bombing Cambodia, an achievement that he later described as the proudest moment of his career, the Thompson Coburn statement said.

The same year he also introduced the landmark War Powers Act which required the US president to seek Congress's approval to go to war - the same act which some senators now want to use to restrict President George W. Bush's war strategy in Iraq.

He retired from the Senate in 1986 at age 57, returning to his hometown to teach, write and practice law.

Eagleton wrote three books, including "War and Presidential Power: A Chronicle of Congressional Surrender," which was published in 1974.

He was working on a memoir of his political career at the time of this death.

Eagleton is survived by his wife of 51 years, Barbara, his two children, three grandchildren, and his younger brother. - AFP/ch