The recent disclosure of memos detailing Supreme Court nominee Samuel A. Alito Jr.'s opposition to abortion rights as a Reagan administration lawyer has created a delicate challenge for the 55-year-old federal appeals judge.

The White House has tried to reassure abortion rights Republicans and moderate Democrats that Alito has an open mind on abortion by pointing to his 15-year record on the bench. That record includes two cases in which he voted to strike down state limitations on access to abortion, and one in which he voted to uphold a restriction.

But the new information adds strong evidence of Alito's personal anti-Roe v. Wade sentiment to the picture.

Now Alito must explain "the possible relationship between these documents and his judicial philosophy, or how his judicial philosophy is separate from these strong statements he makes in the documents," said Michael Gerhardt, a professor of constitutional law at the University of North Carolina at Chapel Hill.

Crucial to Alito's success, legal analysts said, will be his ability to lay out a convincing view of stare decisis -- the legal doctrine that says courts should avoid overturning their past rulings, such as Roe, the 1973 decision that established a constitutional right to abortion nationwide.

He made his first attempt at that on Friday, telling Senate Judiciary Committee Chairman Arlen Specter (R-Pa.), an abortion rights supporter, that "when a matter is embedded in the culture, it's a considerable factor in the application of stare decisis," Specter said at a news conference. Alito said such reasoning could have implications for Roe, Specter noted.

As an appeals court judge, Alito was required to follow Supreme Court precedent. On the Supreme Court, there would be fewer restraints on his decision-making, but stare decisis would be one of them.

Currently, six justices -- including Justice Sandra Day O'Connor, whom Alito would succeed -- have voted on the court to support Roe. Thus, Alito alone could not tip the balance. If Roe were overturned, abortion would not be banned; rather, each state would legislate on the issue as it saw fit.

Chief Justice John G. Roberts Jr. won confirmation in part because the Senate accepted his self-description as a "modest" judge who would approach Roe and subsequent abortion rights decisions with respect and caution, whether or not he thought they were rightly decided.

Ideologically similar to Alito, Roberts had the advantage of a much skimpier paper trail on his personal views of Roe. In 1991, he wrote a brief for the George H.W. Bush administration that suggested in a footnote that Roe should be overruled, but Roberts chalked that up to his role as a lawyer representing a client.

Before the disclosure of the memos, Alito seemed on course to convincing key senators that he would be like Roberts.

But opponents of the nomination say that was undermined by Alito's job application letter to then-Attorney General Edwin Meese III in 1985, in which Alito said he was "particularly proud" of helping the administration argue that the "Constitution does not protect a right to an abortion."

Alito wrote a strategy memo that same year to Charles Fried, solicitor general, outlining an approach to "bringing about the eventual overruling of Roe v. Wade and, in the meantime . . . mitigating its effects."

Alito faces the potentially difficult task of explaining that he is still the man who wrote the Reagan-era memos, but a man whose views have been tempered both by his experience as a judge and by subsequent developments in the law. And he must do this without alienating antiabortion conservative Republicans.

In Alito's defense, White House officials have argued that he was merely advising a client in the memo to Fried, and that the best predictor of what kind of justice he would be is his 15-year judicial record. Alito echoed that point in his meeting with Specter on Friday.

Of the two arguments, the second is probably the stronger, legal analysts said. As a judge, Alito voted in 2000 to strike down a New Jersey ban on what its opponents call "partial birth" abortion and, in 1995, to strike down what abortion rights advocates saw as Pennsylvania's onerous regulations on federally funded abortions for victims of incest or rape. Both times, Alito bowed to controlling Supreme Court decisions; and in the 1995 Pennsylvania case, he resisted a fellow conservative judge's dissenting opinion that would have upheld the abortion regulations.

Alito's memos, analysts noted, were written 12 years after Roe was decided and seven years before the Supreme Court's landmark 1992 reaffirmation of Roe in Planned Parenthood v. Casey. Today, Roe is much more deeply entrenched in the law.

"More telling is that as a judge, when it came time to apply the law, Alito applied the law," said Peter Berkowitz, an associate professor of constitutional law at George Mason University.

Abortion rights advocates and some of their Senate allies have argued that Alito's 1985 writings prove that he cannot make that case. They say he has a personal anti-Roe agenda that showed in his 1991 dissenting opinion in favor of a Pennsylvania law that would have required married women to notify their husbands before getting an abortion. The Supreme Court rejected his view by a 5 to 4 vote in 1992.

Alito may not help his cause by trying to distance himself from the letter to Meese, Gerhardt said. If Alito vows to follow stare decisis at his hearings next month, Gerhardt noted, "Senators can ask, 'Are you simply saying that just because you're applying for another job?' "

Hearings on Samuel A. Alito Jr.'s nomination are to begin in January.