WASHINGTON -- Pennsylvania Sen. Arlen Specter has long touted his skills as a prosecutor and as an abortion-rights advocate, and in yesterday's hearing he once again took a leading role in questioning Supreme Court nominee Samuel A. Alito Jr. about the divisive issue of abortion.

But some members of Democratic and liberal groups, who were so pleased when Mr. Specter launched the hearings for now-Chief Justice John G. Roberts Jr. with tough questions about his views on abortion, complained yesterday that Mr. Specter was less aggressive in questioning Judge Alito and at times was acting as more of an advocate for the nominee than as an impartial judge.

The Judiciary Committee chairman's line of questioning yesterday in the more than 20 minutes he spent on abortion was similar to the road he had taken with then-Judge Roberts.

Mr. Specter established, as he had at the Roberts hearing, that Judge Alito believes that the U.S. Constitution does recognize a right to privacy and that it extends to decisions about contraception -- an underpinning of the Roe v. Wade decision upholding abortion.

But while then-Judge Roberts told Mr. Specter that when the court overrules a precedent, "it is a jolt to the legal system" and that the Roe ruling "is settled as a precedent of the court," Judge Alito offered more general pronouncements about the importance of the stare decisis doctrine, which holds that judges should consider precedent as an important factor in maintaining stability in the law.

But the current nominee also emphasized repeatedly, to the alarm of abortion-rights groups, that he did not believe that the doctrine was "an exorable command."

When Mr. Specter asked Judge Alito specific questions about another abortion case, the 1992 Planned Parenthood v. Casey decision -- such as whether he agreed that overturning Roe could raise questions about the legitimacy of the court -- Judge Alito said simply that the legitimacy of any court would be undermined if a court made decisions "based on its perception of public opinion."

Some of the groups said they had hoped that Mr. Specter would question Judge Alito more closely about a statement he made on a 1985 job application: that, in his view, the Constitution does not provide a right to an abortion.

Judge Alito said it was an accurate representation of his views at the time, and Mr. Specter seemed satisfied with the nominee's response that he would look at abortion questions with an open mind as a justice. But Democrats later challenged Judge Alito to elaborate.

So Mr. Specter surprised abortion-rights groups yesterday when he said Judge Alito's remarks went farther than then-Judge Roberts had regarding the abortion issue and that the current high-court nominee had set a new standard in answering questions during his confirmation hearings.

On abortion, Mr. Specter said Judge Alito "dwelt quite extensively on the precedent issue. ... He went as far as he could."

Asked whether he was concerned that Judge Alito had not said Roe v. Wade was settled law, Mr. Specter said he didn't expect the nominee "to state how he is going to decide the case if the issue comes before him and talk about it as settled law. That would be tantamount to saying how he's going to decide the case."

Representatives of both pro- and anti-Alito camps said they were surprised by Mr. Specter's more-muted role in this round of hearings.

"Specter asked no follow-up questions," said Nan Aron, President of the Alliance for Justice, which is opposing Judge Alito. "The particular answers he did get -- which, for a pro-choice senator, must have been problematic -- he simply went on to the next question. ... With Roberts, he at least went through the motions of following up."

Tony Perkins of the conservative Family Research Council said he wasn't sure which direction the chairman was going with his questions. "He did seem to be friendly toward Judge Alito," Mr. Perkins said. "Sometimes you'd think he was being defensive for Alito; other times he was aggressive in defending abortion rights. I was left uncertain."

Mr. Specter's strongest defense of Judge Alito came toward day's end, when he said Judge Alito had topped even then-Judge Roberts in being forthcoming with his answers.

Mr. Specter has often said the "dance" between Supreme Court nominees and senators is subtle minuet in which nominees answer just enough questions to be confirmed. But he said Mr. Alito had set a higher bar yesterday. "I think the dance pattern has changed," the chairman said. "I was trying to think of an appropriate reference. Maybe the foxtrot."

A number of Democrats, by contrast, criticized Judge Alito's answers as vague and inconsistent. The Judiciary panel's ranking Democrat, Sen. Patrick J. Leahy of Vermont, held up Chief Justice Roberts' replies as a model, stating that his consistent answers "helped build a record that gave many of us who voted for him the confidence in his candidacy that we needed."