She is a handsome, spirited, brilliant achiever with a dazzling portfolio that includes two Cabinet posts. For years, people told her that she could become mayor of Washington by merely lifting a finger. But with the primary just 20 days away, candidate Patricia Roberts Harris is lagging behind incumbent Marion Barry, whose followers give him no better than a "so-so" rating.

In her campaign office on K Street NW this week, Harris was remembering the big businessman, the lawyer and the clergyman who, before she took the plunge, importuned her to save the city.

The businessman has since endorsed Barry. So has the lawyer, who commissioned a poll that showed she would walk away with the election. The minister joined other members of the black clergy backing Barry. When she asked for explanations -- and she is very direct about this sort of thing -- she got back mumbles about "not rejecting male black leadership."

"Talk about Teddy Kennedy," she said dryly.

In 1980, Sen. Kennedy was hearing that he must save the party, that he would cream Jimmy Carter. But once he stepped out, the margins and allies melted.

Arthur J. Goldberg, another public figure with a stellar past, who was lured into a hapless race against Nelson Rockefeller for governor of New York, warned Harris to "stay out of drafts."

But she decided last April that "Marion was doing a terrible job and that the city needed someone with the right kind of values." Since then, she has been learning that her kind of excellence strikes some people as threatening and that the voters are, in her words, "extraordinarily forgiving of Marion Barry."

She hasn't given up. She campaigns early and late, a stylish figure in the early mornings at Metro stops, holding out her hand to sleepy-eyed commuters and saying, "Good morning, I'm Pat Harris, and I want to go to work for you as your mayor." Everyone recognizes her, some with gratitude. A Metro driver fervently wishes her luck.

Barry is somewhat surprised that he is so effortlessly overcoming the challenge from on high. He goes to a rally in the party room of an upper Connecticut Avenue apartment house before an audience mixed as to age and race and says it is a matter of experience: "There is no better qualification for being mayor than having been mayor."

On the way out, followed by a large entourage, he says jauntily, "Pat underestimated my strength. Her organization is a disaster. Local experience is different from national. If you're a Cabinet officer, you get your budget handed to you. If you're mayor, you have to find the money. Urban government is potholes, not policy."

He turns aside Harris' newest bid for a two-person debate. There are two other candidates -- City Council members Charlene Drew Jarvis and John Ray -- but the fight has narrowed to the mayor and Harris.

"I won't go unless everyone is there," he says, as the police car draws up to escort him to his next stop. "It would be undemocratic."

Harris says she would like to make Washington a show city, where bold new efforts in education and economic development are tried.

"Marion is so proud of his Supercans," she said referring to the mayor's distribution of big, gray plastic garbage cans. "He spent $2.2 million to give them to upper-class people. He should have been planning for solid-waste disposal."

She regards the mayor as "a superb politician." He has even managed to raise the question of her blackness. His campaign manager, Ivanhoe Donaldson, last month designated Barry as "the black candidate in the D.C. election."

"It's a kind of racism," Harris says contemptuously.

She has encountered it before. When she was up for confirmation as Secretary of the Department of Housing and Urban Development, Sen. William Proxmire (D-Wis.) questioned her ability to identify with the poor.

Harris gave an eloquent answer, which she uses in campaign spots: "Senator, I am one of them. You do not seem to understand who I am. I am a black woman, the daughter of a dining-car worker."

But the idea that she has forgotten her own, despite her civil rights record, stalks her. The other day at a meeting, a black woman said to her, "You have always lived white."

"Sometimes you have to think that some blacks resent a certain degree of success," she says carefully.

Her critics say the problem is not Harris' success, but her temperament. "She is divisive, she regards any difference of opinion as a personal attack," said a prominent black woman who is "embarrassed at not supporting a black woman for mayor."

Joseph L. Rauh Jr., Washington's leading liberal, is supporting the mayor. He concedes that not all the rough edges of the old civil rights street warrior have been rubbed off.

"But he's grown from a SNCC [Student Nonviolent Coordinating Committee] kid to a hard-working mayor," says Rauh, who finds Harris too Establishment. They fell out over the Vietnam War, which he bitterly opposed.

All she says with any certainty about what is happening is, "it's bizarre."