In a room at the Justice Department this summer, Harriet Miers listened silently as young lawyers playing senators threw question after question at John G. Roberts Jr. at a secret practice hearing, or "murder board." She watched as he rattled off Supreme Court cases and, as one participant put it, "artfully dodged" inquiries he did not want to answer.

Now it's her turn. After an unexpectedly rocky first week, Miers's nomination to the Supreme Court appears likely to hinge on her performance before the Senate Judiciary Committee at hearings that probably will open early next month, according to strategists in both parties.

The question is how much she learned from Roberts's murder boards and how much constitutional law she can master in cramming sessions over the next several weeks.

Unlike Roberts, who made a career arguing before the high court and commands the nuances of obscure rulings, Miers never practiced that sort of law, nor did she, in her various behind-the-scenes roles at the Bush White House, demonstrate the sort of skill at public performance that Senate hearings demand.

Given her lack of background, lawyers and politicians predict, her hearings could easily turn into a stump-the-nominee contest. And following Roberts, as Sen. Sam Brownback (R-Kan.) put it last week, will be like "following Elvis."

"The hearings for her are the defining moment," said Kenneth M. Duberstein, the former Reagan White House chief of staff who shepherded two Supreme Court nominations through the Senate for President George H.W. Bush. "This is prime time, when America really gets its first look at her and the first time they'll really be listening."

Sen. Charles E. Schumer (D-N.Y.), like Brownback a Judiciary Committee member and expected to be one of Miers's tougher interrogators, said her testimony could determine the outcome. With conservatives disgruntled about her selection and liberals disinclined to support any Bush nomination, Miers faces the prospect of tough grilling from both sides.

"These hearings are going to be crucial -- more crucial than any in a long, long time," Schumer said in an interview. "It's not going to be an easy hearing for Harriet Miers. Roberts was sure of his right flank, and she can't be. And Roberts, of course, is brilliant. No one will be as good. He spent his life doing this. Harriet Miers is a very capable lawyer but is not someone who has spent her life litigating before the Supreme Court."

Bruce Fein, a Republican lawyer who helped prep Sandra Day O'Connor for her confirmation hearings in 1981, put it more bluntly. "It's almost like putting you and me into MCI stadium and saying, 'Play against Michael Jordan at his peak,' " he said. "That's what it's going to be like up there."

Miers, a Southern Methodist University graduate who was President Bush's personal attorney and now serves as White House counsel, may not have Roberts's command of constitutional law, but colleagues predicted she will survive the questioning with relative ease. "Harriet is always thoroughly prepared for everything she does," said her friend Karen P. Hughes, the longtime Bush adviser who now is an undersecretary of state. "I'm confident she will be very prepared, very composed and will make a very strong impression."

In his weekly radio address yesterday, Bush praised Miers as "a remarkable woman and an accomplished attorney" who would be "a good conservative judge" on the high court. "Throughout her life, Ms. Miers has excelled at everything she has done," Bush said. "She's been a leader and a trailblazer for women lawyers, and her work has earned the respect of attorneys across the nation."

The challenge for Miers will be different than for Roberts, who breezed through his hearings and won confirmation last month as chief justice, demonstrating versatility with the issues, even though he resisted giving his own views. Roberts had to explain himself to the party's conservative base, which had some questions about his ideology, but did not have to prove his legal and constitutional credentials, noted Jay Sekulow, chief counsel of the American Center for Law and Justice and an adviser to the White House on judicial nominations. Miers must deal with both.

"The Senate hearings are going to be very important," he said.

Her tentative response to a question during a courtesy call on Capitol Hill last week seemed revealing to some observers. Sen. Patrick J. Leahy (Vt.), ranking Democrat on the Judiciary Committee, asked her to name her favorite justices.

"Warren," she answered, according to people familiar with the conversation.

Leahy was taken aback. Did she mean Chief Justice Earl Warren, the bete noire of conservatives who presided over an activist court? Or maybe his successor, Warren E. Burger, a moderate conservative who voted for Roe v. Wade and rarely makes any scholar's list of top justices?

Burger, she answered.

The Judiciary Committee has not scheduled hearings yet, but officials expect them to be held in early November. They can be arduous even for the most prepared nominee; Roberts spent 22 hours in the witness chair over a week.

While historically many justices had not served as judges, none has been nominated to the Supreme Court since 1971 without experience on the bench, and Miers's career as a Texas corporate attorney has not given her a background in the types of issues that regularly go before the court.

The White House will try to compensate for that with a crash course. She will pore through briefing books on key cases and undergo the same sort of murder boards she supervised for Roberts. The process, which will be run by Rachel L. Brand, head of the Justice Department's Office of Legal Policy, will include former senator Dan Coats (R-Ind.) and former Republican National Committee chairman Ed Gillespie, who will monitor her practices and offer tips on how to answer -- or not answer -- senators' questions.

As a participant in Roberts's preparation, colleagues said, Miers presumably gained not only greater facility with issues likely to be on the agenda but also benefited from helping to refine and revise answers to the toughest questions.

"The great advantage she has is she has the Roberts transcript to study," said H. Christopher Bartolomucci, a former White House associate counsel who participated in a murder board with Roberts. "Not only is that a forecast of the kinds of questions she's likely to get, she can see how they can be answered."

But others suggested the senators would take a different tack with Miers, seeking to demonstrate her unfamiliarity with cases that did not come up during Roberts's hearings.

"If I was a Democrat and I wanted to destroy her candidacy, I'd go to constitutional law professors and experts and get the 60 key Supreme Court decisions," Fein said. The committee members could then go through the list and ask her, " 'Have you read this case from beginning to end?' And when she says for the 59th time, 'No, I haven't,' I'd say, 'Why are you going to be on the Supreme Court?' "

Fein said the White House likely will try to shift the discussion away from legal scholarship and toward biography, much as the first Bush White House did with Clarence Thomas, emphasizing his rise from poverty in Pin Point, Ga. "They'll give her a libretto -- 'you overcame the difficulties as a woman in a masculine world down in Texas,' " he said. "They'll try to paint her as a female Horatio Alger."

The president laid that groundwork in yesterday's radio address, stressing Miers's history as the first woman to be hired at her Texas law firm, the first to become head of a large Texas firm and the first to serve as president of the Dallas and Texas bar associations.

And the White House could try to turn the barrage of attacks on her credentials to her advantage. "One way this actually helps her is it greatly lowers her expectations for the hearings," said a conservative working for her nomination, "and coming on the heels of John Roberts's virtuoso performance, that's actually a good thing. If she exceeds expectations during the hearings, she'll win even more support."

Staff writer Thomas B. Edsall contributed to this report.

Supreme Court nominee Harriet Miers makes a courtesy call on Judiciary's top Democrat, Patrick J. Leahy (Vt.).