Pat Nixon, the uncomplaining silent partner in Richard Nixon's lifetime of political triumph and disgrace, died of lung cancer Tuesday at the couple's home in Park Ridge, N.J. She was 81.

Mrs. Nixon had suffered from lung disease for years and was hospitalized in February for emphysema. Kathy O'Connor, Nixon's aide, said the family had known at least since then that Mrs. Nixon had cancer.In their 53 years of marriage - through the dark years of Watergate, through the pain of his resignation from the presidency - the former Thelma Catherine Ryan was at Nixon's side, never showing in public how much it hurt.

The former president and their daughters, Tricia Nixon Cox and Julie Nixon Eisenhower, were with the former first lady when she died at 5:45 a.m. Tuesday. The Nixons' wedding anniversary was Monday.

"Mrs. Nixon was awake yesterday and knew it was their anniversary," O'Connor said. "The girls were there, and they looked at anniversary cards and beautiful flowers that had arrived for the celebration. She later lapsed into a coma. Mrs. Nixon was a fighter and a very courageous woman."

The funeral will be Saturday at the former president's library in Yorba Linda, Calif. The Rev. Billy Graham, a longtime family friend, will officiate at the funeral, and Senate Republican leader Robert Dole will deliver the eulogy.

Mrs. Nixon will be buried on the grounds of the library, the site of Nixon's birth.

Republican Sen. Mark Hatfield of Oregon stood on the Senate floor to announce Mrs. Nixon's death to his colleagues and pay tribute to "a very gallant lady."

"She was a true effective partner," Hatfield said. "In all the years President Nixon served, she shared the joys. She was the soldier. She was the partner in the fullest meaning of that word."

Mrs. Nixon's health had not been good since that Friday morning in 1974 when a helicopter carried them from the White House into exile. A major stroke in 1976 left her with a paralyzed left side, and Nixon suggested that the sudden illness was linked to her having read "The Final Days," a harsh account of the Watergate scandal.

"Mrs. Nixon read it, and her stroke came three days later," he said. "This doesn't indicate that that caused the stroke . . . but it sure didn't help."

The former first lady made a painful recovery through exercise and physical therapy. But that first stroke - there was another, milder one, in 1983 - began a series of illnesses.

There were repeated hospitalizations for asthmatic bronchitis, bronchial pneumonia and lung infections, and she underwent surgery in 1987 to remove a small cancerous tumor from her mouth. Nixon revealed in a 1993 interview that she also suffered from emphysema. The public didn't know, but she had been a smoker in private.

Mrs. Nixon, a pretty, vivacious woman who met her husband when both were trying out for a part in a play, was nicknamed "Pat" by her father because she was born the day before St. Patrick's Day, 1912.

She shunned public activities after they left the White House and returned to their seaside home in San Clemente, Calif. They lived there until 1980, when Mrs. Nixon decided she wanted to be closer to her grandchildren in the East.

The Nixons' younger daughter, Julie, married David Eisenhower, grandson of the 34th president, and they have three children, Jennie, Alex and Melanie. Tricia married Ed Cox, a lawyer, and they have a son, Christopher Nixon Cox.

"We're just dying out here, slowly," Julie recalls her mother saying in a book about her mother. Moreover, Nixon could no longer stand being hidden from what he liked to call "The Arena," and moved to New York and then to Saddle River, N.J. In 1992, both near-octogenarians, they gave up the spacious house and bought a four-story condominium in nearby Park Ridge.

Nixon emerged from the shadows and traveled around the world, but his wife didn't.

Pat Nixon was a steadfast helpmate to a politician whose career was the most turbulent in the nation's history.

She was at Nixon's side during all his crises - any one of which might have stopped a more resolute man: the secret fund that nearly cost him the vice presidential nomination in 1952; the stoning of his limousine in Venezuela in 1958; the bitter defeats in 1960 for president and 1962 for governor of California; the scorn heaped upon him by anti-war protesters n the Vietnam years.

Pat Nixon maintained a dignified silence during the days of Watergate when Nixon - in his words - was "circling the wagons around the White House," when he was named an unindicted co-conspirator in the attempt to cover up the scandal, when he was denounced before a committee of the Senate and recommended for impeachment by a committee of the House.

"For her, there could be no criticism and no revelation of the despair she may have felt, only support," Julie wrote. "There was no doubt in her mind that Watergate was a political witch-hunt, and that if my father would remain strong, he could withstand it. In the face of blow after blow, she was steadfast. Never before or since has she shown so much strength."

And she stood behind her man in that dramatic hour when Nixon, the only man ever to resign from the nation's highest office, said his emotional farewell to staff and friends in the White House East Room.