Elizabeth Williams Fulbright, 79, the wife of former senator J. William Fulbright (D-Ark.) who was known for her ability to bring grace and humanity to any occasion, died Oct. 5 of congestive heart failure at her home in Northwest Washington.

Mrs. Fulbright, who was married for 53 years to the longtime chairman of the Senate Foreign Relations Committee, was both a tireless campaigner and thoughtful, behind-the-scenes adviser who many said was the senator's greatest asset.

"She was the tremendous humanist," said her daughter, Roberta Foote. "He was the great intellectual. Together they made a great whole."

Mrs. Fulbright was born in 1906 in Philadelphia and educated there at the Agnes Irwin School. She met her future husband in 1930 at a dinner party in Washington and they were married in 1932.

Though raised in a world of society and wealth on Philadelphia's Main Line, Mrs. Fulbright was gregarious and at ease anywhere. She took to campaigning in Arkansas like a native when Fulbright made his first race for Congress in 1942.

And two years later, when Fulbright ran successfully for the U.S. Senate, he and his wife criss-crossed Arkansas together and one columnist wrote for the Arkansas Gazette: "For her to be in politics is just as natural as college boys chasing chorus girls. Regardless of where they are, when Bill stops his hack she jumps out and starts button-holing people with an impassioned plea to the effect that the voters of Arkansas will be unfair to unborn generations if they fail to send her husband to the U.S. Senate."

Her interest in improving international relations grew as Fulbright chaired the Foreign Relations Committee for 15 years, and she was on the board of the International Student House in Washington, which serves as a home to both foreign and American students. There she concentrated on preserving the historic mansion itself and making it a comfortable home for the residents.

Mrs. Fulbright helped arrange tours of the U.S. Capitol for foreign students here under the American Field Service exchange program, often setting up sessions for them with groups of senators in the Senate Caucus Room. She attended functions throughout the years at embassies and made a special point of trying to attend all the national day receptions of other countries.

"She had a completely unaffected graciousness about her," said one longtime friend. "She talked the same to someone cutting her grass as she would to a visiting dignitary and was equally charming to both."

In the 1960s, one newspaper article called her the "most popular Senate wife," a woman who observers said was "smart, hip, kind, flexible, easy-going and thoughtful."

She was a volunteer with the Junior League and a member of the Sulgrave Club, Chevy Chase Club and St. Margaret's Episcopal Church.

In addition to her husband, she is survived by two daughters, Mrs. John Winnacker of Columbia, Mo., and Mrs. Edward T. Foote II of Coral Gables, Fla., and five grandchildren.