WASHINGTON – Senator Schumer laid the groundwork yesterday for stiff questioning of President Bush’s first nominee to the U.S. Supreme Court, Judge John Roberts Jr., dismissing the assertion that previous nominees were allowed to remain silent on controversial issues and settled law, and vowing to take as much time as he needs to determine “who Judge Roberts is, judicially speaking.”

In a Capitol Hill speech aimed at debunking what he referred to as “the Ginsburg myth,” Mr. Schumer said he fears Republicans are providing cover for Judge Roberts to avoid answering questions during next week’s confirmation hearing because of their repeated references to the confirmation hearing of Justice Ginsburg, who declined to answer dozens of questions during four days of testimony in 1993. Mr. Schumer said Justice Ginsburg in fact was expansive and specific in her testimony.

“If Judge Roberts answers important questions forthrightly and convinces us he is a jurist in the broad mainstream, most Democrats will be able to vote for him,” Mr. Schumer said. “If, on the other hand, he chooses evasion over candor, if he uses the mythical ‘Ginsburg precedent’ as some kind of game-show lifeline, we will find it very, very hard to vote for him.”

Mr. Schumer’s speech and his comments to reporters afterward provided an early glimpse of the prominent role he is expected to play in his first hearing on a Supreme Court nomination. Mr. Schumer has long advocated for greater scrutiny of nominees to federal courts, but has waited seven years to exercise the principle on a nominee to the nation’s highest court. Republican supporters of Judge Roberts expect Mr. Schumer to hold nothing back.

“What we expect from him is a lot of grandstanding and a lot of speechifying in the form of question, and a lot of badgering, frankly, in terms of rude treatment of the nominee,” the executive director of the pro-Roberts group the Committee for Justice, Sean Rushton, said. “But I think there probably will be some push back from the Republicans.”

As a member of the minority Democratic Party on the Senate Judiciary Committee, Mr. Schumer will have to defer to a Republican chairman, Senator Specter of Pennsylvania, on procedural matters. Yet Mr. Schumer, who ranks 14th out of 18 members of the committee according to seniority, said yesterday that he has already secured a pledge from Mr. Specter and the ranking Democrat on the committee, Senator Leahy, that he will be allowed as much time as he wants.

“I explicitly asked both Senator Specter and Senator Leahy would I get as many rounds as I needed, and they said yes,” Mr. Schumer said. “So I expect to have many more rounds than two … It’s good and bad to be no. 14. You don’t get our first crack at him, but you can sure do follow-ups.”

According to details of the hearing released by Senate officials yesterday, the first day, next Tuesday, will consist of opening statements by committee members, a formal introduction of Judge Roberts, and an opening statement by Judge Roberts himself. The next day will likely consist of a first round of questions, in which each senator will be allowed 30 minutes. A second round, in which members will have 20 minutes each, is expected to take up the third day. A third, open-ended round will probably take place next Friday.

Officials on the Judiciary Committee said Senator Specter, a notoriously dogged worker who has never before chaired a Supreme Court hearing, is prepared to bring the hearing into next weekend. After questioning, senators will hold a day-long closed meeting to discuss a routine FBI report on the nominee. Mr. Specter intends to hold a committee vote on September 15, in order to give the full Senate a full two weeks to debate the vote ahead of the resumption of the Supreme Court calendar the first week of October.

In pursuing an aggressive line of questioning, Mr. Schumer may have an ally in Mr. Specter, who argued in his 2000 book “Passion for Truth” that senators should “resist, if not refuse” to vote for a nominee who refuses to answer questions on fundamental issues. Indeed, Mr. Schumer cited Mr. Specter’s past statements as justification for the approach he has outlined in public comments on the hearing since Justice O’Connor’s July 1 resignation announcement.

“I think Senator Specter is very sympathetic to the idea that Judge Roberts should answer questions fully and openly,” Mr. Schumer said. “And not just since he became chairman. That’s been a hallmark of his career.”

In another sign that a hearing conducted by Mr. Specter might contain surprises, Judiciary Committee officials said yesterday that the upcoming hearing will feature at least one break from tradition: Witnesses, which have traditionally been heavily weighted in favor of the committee’s majority party, will be greater in number and evenly split. Thirty witnesses are expected to testify.

There was some speculation yesterday that the devastation caused by Hurricane Katrina would force a postponement of the hearing or soften its tone. Ordinarily, a widely watched national event, the hearing is now expected to attract far less attention than was originally anticipated. But Mr. Schumer downplayed the likelihood of either.

“I think we have to proceed on the basis that we can do two things at once,” he said.