WASHINGTON (AP) _ Lani Guinier vowed Wednesday night to fight for confirmation as the nation's civil rights chief despite indications President Clinton was moving toward abandoning her nomination in the face of strong Senate opposition.

In an appearance on ABC's ''Nightline'' program, Guinier disputed critics who claim she favors quotas, and said ''fairness requires that I be given an opportunity to present my views to the Senate'' at a confirmation hearing.

Guinier made her appearance as a senior administration official said Clinton had told senior aides he believes growing Senate opposition had doomed the nomination. ''The president said this nomination had no future,'' the official said, speaking on condition of anonymity. The aide added Clinton did not directly say he would withdraw the nomination, even though that was the implication.

Guinier conceded, ''I really can't tell you what is going to happen'' with her nomination.

She noted, ''The president has been supportive of my nomination. ... The attorney general, Janet Reno, has been enthusiastic about the possibility that I will serve in the Department of Justice.''

''The nomination has proved a lot more complicated than what they anticipated,'' she conceded, ''but I am pleased to be given the opportunity to come on this show to talk to you about who I am.''

While declining to offer a blanket defense, Clinton said Guinier was ''a first-rate civil rights lawyer.'' He said that ''a lot of the attacks cannot be supported by a fair reading of the writings. That's not to say that I agree with everything in the writings. I don't.''

''A lot of what has been said (in the criticism) is not accurate,'' the president told reporters earlier Wednesday. ''On the other hand I have to take into account where the Senate is and I will be doing that and talking to them.''

Clinton did not say what writings he might disagree with.

Guinier's very appearance was part of an unusual campaign to salvage her own nomination. Customarily, appointees to high federal office decline to answer questions until they have faced a Senate confirmation hearing.

Guinier, a 43-year-old law professor at the University of Pennsylvania, has been sharply attacked as a ''quota queen'' and ''far out of the mainstream'' on issues such as affirmative action. Critics say she has espoused extreme race-based positions in her writings on the Voting Rights Act.

Guinier, daughter of black father and white, Jewish mother, said ''my own mother'' wouldn't recognize her from media descriptions of her beliefs of civil rights law. ''I do not believe in quotas,'' she said. ''I do not advocate quotas.

She rejected criticisms that she doesn't believe in majority rule, saying she has no quarrel with it except ''when you have a local majority working in a prejudiced way'' to corrupt the process. In that case, she has advocated remedies requiring ''supermajority'' rule. For example, if four white members of a city council were deliberately rejecting the concerns of the three black members, five votes would be needed for the council to take action.

Guinier and her supporters in the civil rights movement earlier said they thought they could mount a last-minute public relations blitz to revive the nomination's chances, and White House officials had approved that effort.

The ''Nightline'' appearance was part of that effort, even though the Justice Department at one point had prevailed on her to cancel. She also met earlier Wednesday with the editorial boards of The Washington Post and The New York Times.

In an editorial in Thursday editions, the Post said Clinton should not renounce the nomination. ''Mr. Clinton, were he to abandon this nomination at this preliminary stage, would appear not as a born-again centrist but as a president who doesn't know his own mind and runs from trouble,'' the newspaper said.

The White House official said ''the situation is fluid, at least for a day or so,'' but added that the nomination was likely to be withdrawn before the end of the week.

In the opening moments of her appearance, Koppel told her that morning newspaper headlines were flatly predicting the demise of her nomination.

He asked whether she intended to ''go for it with everything you have,'' and she replied, ''That's who I am.

Even so, she declined to answer directly when asked whether the White House told her that it was cool to the nomination, saying at one point, ''I really can't tell you what is going to happen,'' and at another, ''I am here to talk about who I am, and I think that's what the American people would like to hear, finally, who it is that the president has nominated.''

The administration official, who spoke on condition of anonymity, said the prospect of slugging out the nomination battle was raised at the White House meeting attended by Clinton, but advisers cautioned that a president with a 36 percent approval rating does not win such a fight.

Earlier in the day, Clinton had put a question mark over Guinier's nomination, saying he does not agree with all her legal views and will have to weigh the increased opposition from the Senate.

Civil rights groups rallied to Guinier's defense and asked Clinton to do the same.

''We're urging him to stand tall on an excellent nomination,'' Jesse Jackson said at a news conference of two dozen civil rights activists.

Attorney General Janet Reno also renewed her support.

In one comment that has sparked criticism among some senators, Guinier wrote last year, ''In a racially divided society majority rule is not a reliable instrument of democracy.''

In another quotation cited by critics, from an article a year earlier, Guinier wrote, ''Where majority representatives refuse to bargain with representatives of the minority, simple majority vote rules would be replaced.''

Behind the scenes at the White House, officials said the hope was that Guinier would ask to have her nomination pulled.

The furor put Clinton in an awkward position.

Sticking with the nomination could threaten his efforts to boost his low poll ratings by reaching toward the political center.

Yet, withdrawing Guinier would anger allies in the civil rights community and among liberals already unhappy about Clinton's acceptance of deeper cuts in social spending.