The upcoming first-in-a-decade hearings on a Supreme Court nominee will play out before a Senate committee known for partisan clashes and featuring some of Congress's most legendary liberals and ardent conservatives.

Over four days of televised hearings later this summer, the Senate Judiciary Committee will dig for information and frame the debate that will largely determine whether the full Senate embraces President Bush's nominee or splits down the middle, possibly embarking on a filibuster.

Republicans, as the majority party, hold clear advantages. They have 10 committee members, including the chairman, to the Democrats' eight; a larger staff; and 55 of the full Senate's 100 seats. But Democrats have an edge that may loom large in the highly visible, keenly politicized struggle: Their committee members are considerably more experienced and unified than the Republicans. All but two have participated in Supreme Court confirmations, and those two -- Charles E. Schumer (N.Y.) and Richard J. Durbin (Ill.) -- are glib, media-savvy lawyers.

By contrast, only three of the 10 Republicans have handled a Supreme Court nomination. Party veterans who oversaw past Supreme Court confirmations, such as Strom Thurmond (S.C.) and Alan K. Simpson (Wyo.), have been replaced by greener members.

"The gravitas gap will be an issue if Democrats decide to go to the mat about somebody," said Howard M. Wasserman, a law professor at Florida International University in Miami. "The experience that senators have on the Democratic side . . . could affect the tone of the hearings -- respectful, but tough, inquisitorial."

The Republican members constitute an unwieldy mix of ardent abortion foes, consensus-seeking mavericks and mainstream party loyalists. And they are led by one of the most controversial Republicans, the 75-year-old chairman, Arlen Specter of Pennsylvania.

Reviled by some conservatives for his centrist views and support for abortion rights -- and admired by many moderates for his sharp mind and independent spirit -- Specter vows to keep the hearings dignified, focused and as bipartisan as possible. "All nominees will be given a full chance to answer," he said. "This is not a courtroom."

Some analysts view the committee's makeup and personalities as a potential recipe for discord, not only between the two parties but also perhaps within the GOP ranks. Sens. Sam Brownback (R-Kan.) and Tom Coburn (R-Okla.) strenuously differ with Specter on abortion -- certain to be a prime issue during the hearings. And the president's allies make no secret they would prefer the gavel to be back in the hands of Orrin G. Hatch of Utah, the panel's most senior Republican and a steadfast Bush loyalist. Party term-limit rules forced him to step aside just before the high court vacancy occurred.

Specter, undeterred, said he does not see himself as an arm of the White House nomination machinery but as part of a separate branch of government charged with carrying out a dignified but objective hearing. "They can do their spinning," he said in an interview last week.

His battle with Hodgkin's disease, which has involved chemotherapy that has left him gaunt and temporarily bald, will not slow him down, he added. "I've looked cancer in the face," he said. "I don't feel great when I get up in the morning. But I'm ready."

As for his hair, he has been told it will grow back within six months -- "even thicker!" he said with a droll laugh.

Sandra Day O'Connor's retirement sent committee members and their staffs into a rare summer overdrive. Specter's hearing preparations are being headed by Michael E. O'Neill, an associate professor at George Mason University School of Law, who took a leave of absence to be chief counsel to the Judiciary Committee. O'Neill has read every word of the past 11 hearings in preparation.

Specter plans to try to discourage repetitious questioning, according to his staff. "People try to ask, 'Are you going to vote to uphold Roe v. Wade?' in 150 different ways," said one Specter aide. " At what point is it . . . badgering the witness?"

A top Democratic aide, hardly alone, canceled a long-planned vacation to Italy. If Chief Justice William H. Rehnquist, who is fighting cancer at age 80, also resigns as many expect, the committee will stand at the center of the first multiple-vacancy nomination since 1986.

No problem, said Specter: "We're like the Pentagon. We're always ready for a two-front war. Or three fronts!"

Past Hearings Loom Large

If Americans have any image of the Judiciary Committee, it probably stems from the riveting 1991 broadcasts of law professor Anita Hill's sexual harassment allegations against Clarence Thomas, who declared the Supreme Court confirmation proceedings "a high-tech lynching for uppity blacks." Farther back in time, but still painful to conservative activists, was Robert H. Bork's contentious 1987 hearing that led to his defeat on the Senate floor.

Specter played big roles in both cases. He grilled Bork and was one of six Republican senators to vote against him, drawing the enduring enmity of many staunch conservatives. Four years later, he questioned Hill so aggressively that some conservatives forgave him, but women's groups denounced him.

Since the incendiary Thomas hearings, which inspired a "Saturday Night Live" skit, the Judiciary Committee's activities have rarely penetrated popular culture. The committee unanimously recommended Ruth Bader Ginsburg in 1993 and Stephen G. Breyer in 1994, and they comfortably won Senate confirmation to the Supreme Court.

In the intervening 11 years, the Internet, bloggers and round-the-clock cable TV news have become mainstays of American politics, and groups on the left and right have raised millions of dollars to pour into trying to influence the next Supreme Court contest. Soon after Bush announces his nominee, the committee's eight Democrats and their party leaders will have to decide whether to mount an all-out battle reminiscent of the Bork hearing, or settle for the more placid atmosphere of the Ginsburg and Breyer confirmations. In those days, it was the Democrats who controlled the House, the Senate and the White House.

The eventual nominee's testimony, and evidence presented to the committee, obviously will help determine the hearing's tone and outcome. Meanwhile, activist groups will cite emotional issues such as abortion and same-sex marriage as they urge both parties toward full-scale war.

Mavericks in the Ranks

The committee's Democrats are anchored by five generally liberal lawyers who comfortably debate politics and the law in hearing rooms and on TV. Their mission is to expose the nominee's political philosophies and lead the party's opposition if they are deemed too conservative.

Three Democrats have a combined 96 years on the panel: Edward M. Kennedy (Mass.), Joseph R. Biden Jr. (Del.) and Patrick J. Leahy (Vt.).

Leahy, the panel's ranking Democrat, has forged a cordial bond with Specter, unlike the testy relationship he had with Hatch. The two men talk almost daily, Leahy said, and they are determined to keep interest groups or unreasonably partisan senators from hijacking the nomination process.

"We know the Senate has to stand up here," Leahy said in an interview Friday. He vowed to press nominees to explain their views on contentious issues and to grill those who profess to be blank slates. "If I'm not satisfied with the answers," he said, "I'm not going to vote for that person, no matter who it is."

Three committee Democrats -- Dianne Feinstein (Calif.), Russell Feingold (Wis.) and Herb Kohl (Wis.) -- usually have lower profiles. Despite 16 years on the panel, Kohl is quiet, and is usually a reliable party-line voter. Feinstein and Feingold tend to break party ranks more often, sometimes in unpredictable ways. If Democrats are to split on the nomination, the first signs may appear in Feingold's and Feinstein's questions and body language, said congressional scholar Ross Baker of Rutgers University, an expert on the Judiciary Committee.

Among the Republicans, only Specter, Hatch and Charles E. Grassley (Iowa) have handled Supreme Court nominations. Grassley is a party loyalist, but he focuses mainly on his work as Finance Committee chairman.

Senate insiders said to look for the panel's outspoken conservatives, Coburn and Brownback (a possible presidential candidate), to lead the antiabortion argument. Coburn, a physician, caused a political uproar during his 2004 campaign by saying in an interview, "I favor the death penalty for abortionists and other people who take life." Reliably mainstream conservatives on the panel include Hatch, Jon Kyl (Ariz.), Jeff Sessions (Ala.) and John Cornyn (Tex.).

Cornyn said that although any senator is "at liberty to ask any question," he views it as "the obligation of the nominee not to answer certain types of questions." Republicans point to the precedent of the confirmation hearings for Ginsburg and Breyer, who declined to comment on legal issues that might come before the court.

Two of the more unorthodox GOP members are Lindsey O. Graham (S.C.) and Mike DeWine (Ohio). Both said they would vote to ban judicial filibusters if Democrats continued blocking Bush's court appointees. But they were among seven Senate Republicans -- and the only Judiciary Committee members -- to sign a May 23 bipartisan pact that averted a filibuster showdown, at least for now.

Overseeing the bunch is Specter, among the GOP's most independent and unpredictable senators. He cited Scottish law in voting "not proven" at Bill Clinton's impeachment trial.

Specter's iconoclasm nearly cost him the chairmanship last fall, when he said a Supreme Court nominee openly opposed to abortion rights would have a hard time being confirmed. Conservatives howled, and Specter had to scramble, promising Bush prompt committee hearings and votes on his nominees.

Some congressional scholars, noting Specter's prickly pride, doubt the episode will inhibit his independent tendencies. "One does not force Arlen Specter to grovel without paying a substantial price," said Rutgers' Baker. Even if Specter irritates his conservative colleagues again, "it would be harder to purge him now," Baker said, because the nomination process is underway and his illness makes him a more sympathetic figure.

Research editor Lucy Shackelford contributed to this report.

Sen. Arlen Specter (R-Pa.) will chair hearings on a Supreme Court nominee.