The Senate hearings set to begin this morning on President Bush’s latest nominee to the Supreme Court, Judge Samuel Alito Jr., are likely to be bruising and fractious, with a Democratic filibuster to block his nomination a live possibility.

A member of the Judiciary Committee, Senator Feinstein, said yesterday that she is gravely concerned about Judge Alito’s views on abortion rights and his statement, in a 1985 job application, that he was proud of his legal arguments that the right to an abortion is not protected by the Constitution.

“I’m old enough to know what it was like back when abortion was illegal,” the Democrat of California said on Fox News.” I know what it’s like to see young women commit suicide. I know what it’s like to see them go to Tijuana. And I don’t want to go back to those days.”

Asked if she would filibuster the nominee if the hearings establish that he would overturn the Supreme Court’s landmark 1973 abortion ruling, Roe v. Wade, Mrs. Feinstein said, “If I believed he was going to go in there and overthrow Roe? … Most likely, yes.”

In a separate television interview, Senator Schumer raised the specter of a filibuster against Judge Alito without being asked. “I haven’t made up my mind about how to vote and certainly whether to block him or not, whether to urge my colleagues in the caucus to filibuster,” the senator, a Democrat, told NBC.

The chairman of the Judiciary Committee, Senator Specter, said he also wants to hear more about Judge Alito’s views on abortion. Mr. Specter, a Republican of Pennsylvania who favors abortion rights, pointedly declined to commit to vote in favor of the nomination, but he said there was nothing about the nominee that could justify a filibuster.

“I do not see any rational basis for filibustering Judge Alito,” Mr. Specter told CNN.

During interviews on Sunday talk shows, several senators said they plan to question Judge Alito about his views of executive power, particularly in light of the recent disclosure that Mr. Bush authorized a National Security Agency program to monitor international phone calls and e-mails of Americans without court approval.

Mr. Schumer said a speech Judge Alito gave to a conservative legal group, the Federalist Society, suggests that he has an expansive view of the power of the presidency. “He said he believed in the unitary executive. That means the executive has all the power,” the senator said. “It would mean you couldn’t have a 9/11 commission. It might mean in a time of war, relevant to today, that you could have warrants issued so you could go into someone’s home without going to a judge. These are things that edge on the extreme.”

Another issue that has roiled preparations for the hearings is Judge Alito’s membership in a conservative group of Princeton graduates, the Concerned Alumni of Princeton. He noted the affiliation on the same 1985 application for a Justice Department post, but gave a written statement to the Judiciary Committee last month that he had “no recollection of being a member” or having any other affiliation with the group, which was founded in 1972.

In an interview yesterday with ABC, Mr. Kennedy called the alumni group “anti-black, anti-disabled, and anti-women.”

Democrats on the Senate Judiciary Committee had planned to call a strident critic of the Concerned Alumni of Princeton, Stephen Dujack, as a witness at this week’s hearings. However, they reversed course on Friday and pulled Mr. Dujack’s name from the witness list. The move followed a flurry of attention on the Internet and elsewhere to an opinion piece Mr. Dujack wrote in 2003 in which he equated the treatment of farm animals with the suffering of the Holocaust.

In an interview yesterday, Mr. Dujack declined to discuss how or why he was disinvited. “Neither the Democrats on the committee nor I are talking about it,” he said.

Mr. Dujack said the animal-rights article he wrote was “misrepresented,” but that he regretted the distress it caused to Holocaust survivors and their families. “I certainly have apologized for it and I should have apologized for it a long time ago,” he said.

Mr. Dujack said the piece was aimed at explaining the vegetarian principles of a Nobel prize-winning author who was also his grandfather, Isaac Bashevis Singer. He once wrote that many animals live in “an eternal Treblinka.”

“It bothers me that I upset so many good and decent people in trying to make a point,” Mr. Dujack said.

Mr. Dujack, a Virginia-based journalist who writes primarily about the environment, said he was in the process of preparing written testimony that he plans to provide to the Judiciary Committee about the history of the Concerned Alumni of Princeton. He said Judge Alito can be faulted for continuing to tout his connections to the group long after other alumni cut ties with the organization.

“The reason he can be criticized is that in opposing first the admission of women, of minorities, and later their larger and larger numbers on campus, CAP didn’t just argue against them. It used vicious tactics, including terrible language that was sometime racist and sometime misogynist,” Mr.Dujack said.

One of the founders of the group, T. Harding Jones of Manhattan, said the organization was created in response to a stifling left-wing orthodoxy at the time on the part of student groups, the faculty, and the university leadership. “The reason for the founding was we felt there was no serious political debate on campus,” Mr. Jones said in an interview. “The alumni weekly was so closed to serious discussion on any of these changes that were happening. As alumni, we were really being cut out of what was happening.”

Critics of the group have pointed in large part to articles that appeared in its magazine, Prospect, that warn that women and blacks could lower Princeton’s standards and disturb its traditions.

“We published articles we did not necessarily agree with,” Mr. Jones, who edited the publication, said. “Alumni were rightly concerned that rushing into co-education might change” the school, he added. “They just wanted to go slowly for the most part. Affirmative action was intensely discussed all over the country at the time.”

Mr. Jones said Judge Alito had no role with the magazine or the governance of the group and should not be liable for what it published. “It would be outrageous to tar and feather him with any particular thing people might have said in a magazine,” he said.

Senate staffers said they believe Judge Alito may indicate that his concerns about Princeton’s treatment of the military’s Reserve Officer Training Corps could have led him to the conservative alumni group. The possibility that the nominee would offer such an explanation was first floated last week by a gossipy Web site, the Drudge Report.

“There was a serious discussion of getting rid of “the military training program, Mr. Jones said. “We published articles in favor of keeping ROTC on.”

Judge Alito took part in the military training program before graduating from Princeton in 1972. He served briefly on active duty in the Army after graduating from Yale Law School in 1975.

Asked if ROTC could explain Judge Alito’s affiliation with the alumni group, Mr. Dujack said, “Certainly, it’s plausible. A lot of people joined CAP for different reasons, although it was mostly about the fact Princeton admitted women and minorities.”

Mr. Dujack noted that a former senator of New Jersey, Bill Bradley, was once a member but cut his ties to the group in 1973. Senate Majority Leader Frist, a Princeton trustee at the time, wrote a report sharply critical of the conservative alumni group.

Mr. Dujack disputed Mr. Jones’s claim that the alumni bulletin was closed to right-wing views. “The allegations are totally false,” said Mr. Dujack, who edited the publication for a time in the 1970s.”They didn’t come to us with things to publish that were turned down.” He said Mr. Jones and other leaders of the conservative group refused offers to meet with Princeton officials on campus, insisting that any meeting take place in Switzerland.