It was evidently the right idea at the right time, and it hit a responsive chord both with the Washington artists who generously gave of their talents and with the Christmas shoppers who recognized a bargain when they saw one. Washington artist Jody Mussoff decided she wanted to do something to benefit the AIDS program at the Whitman-Walker Clinic in Adams-Morgan. Since her association was mostly with fellow artists, she decided they might be the key to a fundraiser. She talked with Komei Wachi, owner of Gallery K on P Street, about using his space and selling donated works from local artists for only $100 each.

Wachi agreed, and more than 130 artists, including Tom Green, Polly Kraft, Tom Dineen, Sidney Lawrence, Fred Folsom, Joe Shannon and Manon Cleary, responded. By 7:30 a.m. Sunday the first potential buyer was at the door of Gallery K, and, by the time Wachi opened for business at noon, about 300 were standing in a line stretching almost to Dupont Circle.

Within two hours, Mussoff said, nearly everything was sold. Sometime later this week she will take a pile of checks from the sales and donations amounting to $12,500 to the clinic to be used for its housing, counseling and financial-aid program. The Most Influential Women

The annual survey of 1,700 editors and reporters from newspapers across the country has listed Washington Post Co. Chairman Katharine Graham as the most influential woman in America. In the list of the 25 most influential women who "have the strongest effect on both public policy and public opinion," astronaut Sally Ride came in second and Supreme Court Justice Sandra Day O'Connor and First Lady Nancy Reagan tied for third.

Olympic gymnast Mary Lou Retton was fourth and Kennedy Center honoree, diva Beverly Sills, and Transportation Secretary Elizabeth Dole tied for fifth. Others on The World Almanac and Book of Facts list, in order, were: former vice presidential candidate Geraldine Ferraro; former U.N. ambassador Jeane Kirkpatrick; tennis player Chris Evert Lloyd and founder of Mothers Against Drunk Drivers Candy Lightner; columnist Ann Landers; former first lady Betty Ford; tennis player Martina Navratilova; columnist Ellen Goodman and former representative Barbara Jordan; cosmetics queen Mary Kay Ash; actress Jane Fonda; historian Barbara Tuchman; humorist Erma Bombeck; civil rights leader Coretta Scott King; actress Katharine Hepburn; author Judy Blume; advice columnist Abigail Van Buren; and feminist editor Gloria Steinem. McEnroe & O'Neal Expecting

After all the speculation, it's now official. Actress Tatum O'Neal is pregnant and the father, tennis brat John McEnroe, is going to do right by her. He said they plan to marry. In an interview with the Los Angeles Herald Examiner, McEnroe, who is serving a 42-day suspension he incurred at the recent Australian Open, said he denied earlier reports of O'Neal's pregnancy because he wanted to tell his parents about it personally.

McEnroe said they hadn't set a wedding date, and he was "disgusted" with reports that the wedding was to have taken place Nov. 16. When the baby is born, he said, O'Neal and the child will travel the tennis circuit with him. "I'm not going to leave them," he said. End Notes

The condition of Margaret "Peggy" Goldwater, 76, the wife of Sen. Barry Goldwater, was downgraded to serious from satisfactory yesterday. Her leg was amputated nine days ago at midthigh after abdominal surgery three days earlier failed to solve a circulation problem. Goldwater flew to Phoenix early yesterday so he could be with his wife, who is in intensive care at the Good Samaritan Hospital there . . .

Entertainer Eddie Fisher was released from Pembroke Pines Hospital in Florida yesterday, where he had been for three days after nearly collapsing as he prepared to take the stage for a concert . . . Singer Peggy Lee, who underwent open-heart surgery two months ago, was released Monday from the Touro Infirmary in New Orleans and returned to California . . .

More on the "Treasure Houses of Britain," which continues to bring lines of visitors to the National Gallery: At Monday night's special screening of the PBS-TV three-part series on the exhibition at the National Gallery were actors Rex Harrison, Helen Hayes and Jose Ferrer. The Ford Motor Co.-sponsored event was held in honor of Lord Norwich, who is the host/narrator of the series . . .