Daniel Patrick Moynihan, a well-loved, retired Democratic senator from New York died Wednesday from complications following an emergency appendectomy earlier in the month.

"I want to extend my condolences not only to his wonderful family and not only to New Yorkers, who elected him time and time again, increasing majorities from one end of the state to the next, but to our country. We have lost a great American, an extraordinary senator, an intellectual and a man of passion and understanding about what makes this country great," said Sen. Hillary Clinton, D-N.Y., who in 1999 spoke from his farm when she announced her candidacy to succeed him.

"Laura and I are saddened by the death of Senator Daniel Patrick Moynihan," President Bush said in a statement. "Sen. Moynihan was an intellectual pioneer and a trusted advisor to presidents of both parties. He committed his life to service and will be sorely missed."

Moynihan spent his 76th birthday on March 16 in intensive care following emergency appendectomy surgery at Washington Hospital Center the previous Tuesday. His former chief of staff Tony Bullock announced last week that he had developed an infection following the surgery. Bullock said he was suffering from pneumonia and low blood pressure.

Moynihan's wife of 47 years, Elizabeth, daughter Maura and sons Timothy and John were with him throughout his time in the hospital.

The recent ill health followed an intestinal disorder in January and a back injury shortly afterward.

"When it was announced in our caucus that this terrible event occurred you could just see the energy come out of the room and a sadness come on everyone's face," said New York's senior Sen. Charles Schumer.

A former Harvard professor who also taught at Syracuse University following his retirement, Moynihan was highly regarded as an intellect and an expert on welfare reform, transportation initiatives, Social Security and foreign policy.

"The Almanac of American Politics called him the nation's best thinker among politicians since [Abraham] Lincoln and its best politician among thinkers since [Thomas] Jefferson. ... In many respects Pat Moynihan was larger than life," said Sen. Minority Leader Tom Daschle, D-S.D.

"Senator Pat Moynihan tried to help educate this senator, one that needed a lot of help, but he gave me a greater appreciation for our relationship with countries and people all over the world.  This is a giant of a man, a giant of a senator," said Sen. Trent Lott, R-Miss.

A senior scholar at the Woodrow Wilson Center, Moynihan was first elected to the Senate in 1976, and finished his fourth term in 2000. After his retirement, he served on President Bush's Social Security commission.

He has held Cabinet or sub-cabinet positions under Presidents John Kennedy, Lyndon Johnson, Richard Nixon and Gerald Ford. He served as U.S. ambassador to India between 1973 and 1975, and was United States Permanent Representative to the United Nations between 1975 and 1976. At the United Nations, he earned fame among New York voters for his rousing speeches against communism and his unflagging support for Israel.

He used that celebrity status to emerge from a five-way primary and defeat Republican James Buckley for New York's Senate seat, claiming in ads: "He spoke up for America. He'd speak up for New York."

Moynihan worked in the Labor Department in the Kennedy administration, and almost immediately found himself at odds with J. Edgar Hoover's FBI over an article he'd written about the mafia.

An internal agency memo called Moynihan "an egghead that talks in circles." At the bottom of the memo, Hoover scrawled, "I am not going to see this skunk."

A self-described liberal, Moynihan was struck when he was accused of racism for suggesting in a 1965 report to President Johnson entitled "The Negro Family: The Case for National Action" that the rising rate of out-of-wedlock births threatened the stability of black families.

In President Nixon's administration, he proposed a policy of "benign neglect" toward minorities that also drew heavy criticism.

As a senator, Moynihan championed many of the liberal Democratic programs he had questioned, including public jobs programs and federal aid to New York, which was suffering from crushing welfare rolls. In 1988, he led the fight for the Family Support Act, a major revision of the nation's welfare laws.

Born in Tulsa, Okla., Moynihan was the eldest of three children who helped his mother raise his siblings after his father deserted the family when Moynihan was just 10.

He spent his early childhood in Indiana, before moving to New York City. There he worked as a shoe-shine boy to help pay the bills. As a teenager, he was shining shoes in Central Park when he heard that Pearl Harbor had been attacked.

Moynihan graduated from high school, worked on the docks and attended City College. After a stint in the Navy, he went on to college at Tufts on the G.I. Bill. He also attended the London School of Economics with a Fulbright scholarship.

Moynihan and his family frequently spent summers in an old one-room schoolhouse in the upstate hamlet of Pindars Corners where he liked to write.

Fellow legislators had named Manhattan's new federal courthouse in his honor.

The Associated Press contributed to this report.