WASHINGTON – Supreme Court nominee Samuel Alito can expect severe questioning from a bloc of Democrats on the Senate Judiciary Committee this week in a confirmation hearing that promises to be the most openly partisan in nearly two decades. The committee will begin a grueling three days of questioning today on issues ranging from abortion to civil liberties to Judge Alito’s past association with conservative groups.

In particular, Democrats are expected to zero in on a handful of decisions and a 1985 job application by the 55-year-old federal appeals court judge in an effort to cast him as routinely siding with corporations over employees, presidential power over civil liberties, and majorities over minorities. They also will question Judge Alito’s integrity by citing his participation in a case that involved a mutual fund company in which he had invested.

Democrats made their case against Judge Alito before questioning began, outlining their concerns in 10-minute opening statements. They said Judge Alito faces heightened scrutiny because of the seat he has been asked to fill. Justice O’Connor, who is retiring, has been the swing vote in roughly three-quarters of the 5-4 decisions on the Supreme Court since 1995. Yet one after another, they portrayed Judge Alito’s 15-year judicial record as extreme.

“Judge Alito, in case after case after case, you give the impression of applying a careful legal reasoning, but too many times you happen to reach the most conservative result,” Senator Schumer, a Democrat of New York, said. “You give the impression of being a meticulous legal navigator, but in the end, you always seem to chart a rightward course.”

Twenty-two Democrats voted for Chief Justice Roberts, who replaced a conservative on the bench. But the minority party is likely to yield fewer votes for Judge Alito, who was nominated after a previous choice to replace Justice O’Connor, Harriet Miers, withdrew. Mr. Schumer said Judge Alito’s burden is “triply high” because of the seat he has been asked to fill, the circumstances that led to the withdrawal of Ms. Miers, and his judicial record.

Republicans, meanwhile, charged Democrats with applying a new standard to Judge Alito, and they pledged to defend him throughout the hearing. The committee’s chairman, Senator Specter, of Pennsylvania, described opening statements by Democrats as “indictments.” He said Democrats offered a “very selective reading” of Judge Alito’s opinions, and he called on his colleagues to “give the man a chance to speak his piece.”

Some Republican advocates said they were particularly upset by the opening statement of Senator Kennedy, a Democrat of Massachusetts. They cited Mr. Kennedy’s assertion that Judge Alito has not written a single opinion favoring a minority who had alleged race discrimination on the job. Soon after the comment was made, Republican staffers circulated a document listing four occasions in which Judge Alito had sided with a minority in such a case.

“Everything is pretty much what we expected, except that Kennedy is far worse than we expected,” the legal counsel for the Judicial Confirmation Network, Wendy Long, said. “I mean he was just way off the reservation. You expected some of the others to set up questions that they will ask later on, but Kennedy’s statement was different in kind. He just misstated the facts about Alito’s record.”

Several Democrats raised concerns about Judge Alito’s stated support, during a 2000 Federalist Society convention, for broad presidential powers. Citing a recently disclosed National Security Agency surveillance program, they said they fear Judge Alito might give the president a blank check to spy on Americans. Senator Feingold, the lone member of the Senate to vote against the Patriot Act in 2001, said that Judge Alito’s “instinct seems to be to grant prosecutors whatever they seek.” Mr. Feingold, of Wisconsin, voted in favor of Chief Justice Roberts.

Judge Alito’s past professional and academic associations will also come into play. On his application for a job in the Department of Justice in 1985, Judge Alito said he was a member a member of Concerned Alumni of Princeton, a group that criticized what it viewed as eroding admissions standards and which is said to have raised questions about opening up admission to women. Judge Alito said in a recent Judiciary Committee questionnaire that he does not recall being a member of the group. Mr. Kennedy chose to believe the earlier statement of admission, calling it “troubling.”

A veteran of several Supreme Court hearings and the president of the liberal organization People for the American Way, Ralph Neas, said he expects the hearing to be contentious. Mr. Neas helped sink a conservative nominee from the Reagan administration, Robert Bork, in 1987.

“I think it’s going to be a very spirited exchange for the next several days,” Mr. Neas said. “I think the Democratic senators made clear that the burden is on the nominee and that they have a lot of concerns and a lot of doubts based on his judicial record and his time at the Department of Justice.”

Mr. Specter, who voted against Mr. Bork in committee, said he has not decided on Judge Alito. Yet, in citing the recommendation of several other judges, Mr. Specter seemed inclined toward this nominee. He also secured an endorsement of Judge Alito from a former governor of New Jersey, Christie Todd Whitman, following her introduction of Judge Alito to the committee.

Ms. Whitman, a Republican, is a strong supporter of abortion rights. She opened her remarks to the committee by saying she urges them to confirm Judge Alito.

Judge Alito sat through more than three hours of statements, largely expressionless, before taking an oath and delivering an 11-minute statement in which he credited his parents for his accomplishments and his simple New Jersey upbringing for his outlook. He pledged commitment to the rule of law, saying “a judge can’t have an agenda.” In a possible oblique reference to his association with Concerned Alumni of Princeton, he described his time in college as “a time of turmoil” during which he saw “some very smart people and very privileged people behaving irresponsibly.”

In facing a bloc of Democrats who have already expressed an intention to grill him on his personal views on abortion, presidential power, and other issues, Judge Alito will have to display an equanimity similar to Chief Justice Roberts. Some people who have been briefed on Judge Alito’s mock hearing sessions have expressed concerns about his tendency to grow defensive.

But yesterday, he showed little sign of that. And at one point, when Mr. Kennedy described his record as “disturbing,” Judge Alito’s wife, Martha-Ann, winked at a friend nearby and smiled.