WASHINGTON - Daniel Patrick Moynihan, a former Democratic senator, ambassador and presidential adviser known for his scholarly intellect, has died. He was 76.

"In many respects, Pat Moynihan was larger than life," said Senate Democratic leader Tom Daschle, leading tributes on the Senate floor to the man who from 1977 to 2001 was one of the body's most beloved and respected members.

Sen. Hillary Rodham Clinton, who two years ago succeeded Moynihan in the New York Senate seat, announced his death on the Senate floor. "We have lost a great American, an extraordinary senator, an intellectual and a man of passion and understanding for what really makes the country work," she said.

Moynihan died Wednesday at the Washington Hospital Center from complications stemming from a ruptured appendix. In declining health recently, he had undergone surgery to have his appendix removed on March 11.

During his 24 years in the Senate, lawmakers from both parties turned to the gangly, professorial Moynihan for his expertise on welfare issues, transportation, Social Security and foreign policy.

"Rising from the depths of Hell's Kitchen in New York," said Senate Majority Leader Bill Frist, R-Tenn., "he became one of America's true leading intellectuals, whose foresight and whose ability brought to public attention a mass of critical issues long before others even realized these issues existed."

"I just hope God gives us a few more Pat Moynihans in this Senate, and in this country," fellow New York Democrat, Sen. Charles Schumer, said.

In 2000, Moynihan received the Presidential Medal of Freedom, the nation's highest civilian honor.

Born March 16, 1927, in Tulsa, Okla., he became a shoe shine boy in New York City to help make ends meet after his father deserted the family when Moynihan was 10. He graduated from Benjamin Franklin High School in East Harlem and attended the City College of New York for one year before enlisting in the Navy, serving on active duty from 1944 to 1947.

He later graduated from Tufts University, studied at the London School of Economics as a Fulbright Scholar and taught government at Syracuse University and Harvard University. He was the author or editor of 19 books.

He was named an assistant labor secretary in the Kennedy administration and went on to become the first person ever to serve in a Cabinet or sub-Cabinet position in four consecutive administrations, from Kennedy through Ford.

As President Nixon's urban affairs adviser, he proposed a policy of "benign neglect" toward minorities that drew heavy criticism. A 1965 report to President Johnson created a major policy flap when he warned that the rising rate of out-of-wedlock births threatened the stability of black families.

Moynihan saw himself at the time as a liberal observer warning of future problems. Rather than hearing praise, he was denounced as promoting racism. The controversy haunted Moynihan for years and resurfaced as late as the 1994 elections.

Rep. Charles Rangel, D-N.Y., a leader of the congressional black caucus, said Wednesday that Moynihan "stood up for the poor, the underserved and the children when they had few other advocates."

There used to be two framed magazine front pages in Moynihan's Senate office. One was The Nation from 1979, titled "Moynihan: The conscience of a neo-conservative." The other was a 1981 issue of The New Republic, "Pat Moynihan, neo-liberal."

Moynihan, said President Bush, was "an intellectual pioneer and a trusted adviser to presidents of both parties." Under Bush, he served as co-chairman of the Commission to Strengthen Social Security.

Moynihan was ambassador to India from 1973 to 1975, and his wife of 47 years, Elizabeth Brennan Moynihan, is an architectural historian specializing in classic Indian architecture. He was U.S. ambassador to the United Nations in 1975 and 1976.

He won the New York Senate seat in 1976, defeating incumbent Republican James Buckley by portraying him as out of touch with New York City's fiscal crisis. But his interests went far beyond state politics, and his fascination with global affairs never waned. At one point he foretold the collapse of the Soviet Union.

"The Soviet Union is a seriously troubled, even sick society," he said in a January 1980 speech on the Senate floor. "The defining event of the decade might well be the breakup of the Soviet empire."

During his years in the Senate, Moynihan became a champion of many of the liberal Democratic programs he had once questioned, defending public jobs programs and fighting to increase federal aid to help offset New York's crushing welfare burden.

In 1988 Moynihan helped bring together conservatives and liberals to enact the Family Support Act, a major revision of the nation's welfare laws.

After retiring from politics, Moynihan became a senior scholar at the Woodrow Wilson Center.

Moynihan, survived by his wife and three children, is to be buried with full military honors at Arlington National Cemetery on Monday.