Arlen Specter, chairman (Pennsylvania)
Years on Judiciary: 24
Attorney and former prosecutor. Independent-minded. Voted against Reagan nominee Robert Bork, alienating conservatives. Grilled Anita Hill during Clarence Thomas hearings, inflaming liberals. Is likely to ask Roberts about "judicial activism" of Rehnquist Court, including decisions to strike down parts of the Violence Against Women Act, which he helped draft. Keeps tight control of the clock.
Quote: "Who are they [judges] to say their method of reasoning is better than ours [Congress's]?"
Orrin Hatch (Utah)
Years on Judiciary: 28
An attorney. Aims to protect nominees from partisan attack. Will note that nominees should not be prejudging cases or answering questions that might reveal a predisposition to rule a certain way. Maintains cordial relations with Democrats, including liberal icon Edward Kennedy.
Quote: "I've talked extensively with Judge Roberts, and I couldn't be more impressed."
Mike DeWine (Ohio)
Years on Judiciary: 10
An attorney. Is one of seven Republican senators to oppose the Senate GOP leadership's plan to outlaw filibusters of judicial nominations. Has drawn opposition from conservatives at home for his willingness to work with Democrats. Is up for reelection in 2006.
Quote: "Roberts is a pro at the highest level. He's had 30 cases before the US Supreme Court, and he knows how to handle himself."
Jeff Sessions (Alabama)
Years on Judiciary: 8
An attorney and prosecutor. Was rejected by the Judiciary Committee for a federal judgeship in 1985. Often uses question periods to counter arguments from the other side of the aisle and to give the nominee a chance to clarify the record.
Quote: "Nominees have often been abused in these hearings and their records misstated. Every nominee should have a fair chance to explain."
Lindsey Graham (South Carolina)
Years on Judiciary: 2
Was an Air Force prosecutor and is currently a reserve judge on the Air Force Court of Criminal Appeals. Played high-profile role in the Clinton impeachment trial. Pushed for investigations of abuses at Abu Ghraib and Guantánamo. Is expected to question Roberts about torture, presidential power, military tribunals, and treatment of enemy combatants. Is a member, along with Senator DeWine, of the so-called Gang of 14, which aimed to avert the need for a change in Senate filibuster rules. Helps make complex legal issues understandable.
Quote: "I want to ask questions average people most want to ask. I'm not here to play gotcha, and my role is not to play cheerleader."
John Cornyn (Texas)
Years on Judiciary: 2
An attorney and former judge on the Texas Supreme Court. Is only panel member with experience on an appeals court. Has evolved into one-man rapid-response operation, rebutting attacks on Bush's judicial nominees.
Quote: "What we need is a fair hearing for a good man and an up-or-down vote by the end of September."
Sam Brownback (Kansas)
Years on Judiciary: 4
An attorney. Is an eloquent critic of abortion rights, genetic testing, pornography, and slavery in places like the Sudan. Social conservatives hope he'll ask tough questions on abortion rights. Is a potential presidential candidate in 2008.
Quote: "I am predisposed to support Judge Roberts, but because he has had limited time on the bench, I want to dig a little bit deeper and ask questions about his overall judicial philosophy."
Patrick Leahy (Vermont)
Years on Judiciary: 26
An attorney and former prosecutor. Worked with White House on USA Patriot Act, but led filibusters against Bush's appeals court nominees. Is expected to insist upon the need to release documents that cover Roberts's years as deputy solicitor general in first Bush administration. A veteran of Senate judicial wars.
Quote: "We are talking about a lifetime appointment that will affect every American and their children and their grandchildren."
Edward Kennedy (Massachusetts)
Years on Judiciary: 42 (a Senate record)
An attorney. Has been Democrats' lead strategist in court-nomination fights since Bork. Formidable questioner. Has a long commitment to civil rights and rights of the disabled, elderly, minorities, and women. His former staff are coordinating judicial fights at Democratic leadership level.
Quote: "[The Supreme Court] is the place where the rights and liberties of the American people are best protected."
Joseph Biden (Delaware)
Years on Judiciary: 28
An attorney. Chaired Judiciary during Bork hearing. Teaches constitutional law. Has rambling style, but asks tough questions and thinks on his feet. Is likely to ask Roberts how far the government can intervene into personal privacy. Is again considering a presidential bid in 2008.
Quote: "Judge [Roberts], I want to know your view of stare decisis as a Supreme Court justice."
Dianne Feinstein (California)
Years on Judiciary: 12
Public official and former mayor of San Francisco. One of five Democrats to vote for Roberts when he came before Judiciary in 2003. First ran for Senate after Clarence Thomas hearings, citing a need for more women on Judiciary. Is looking for assurances on Roberts's views on precedents, such as Roe v. Wade, and privacy rights. Will also question Roberts on federalism, the commerce clause, and Congress's ability to regulate the environment.
Quote: "To stonewall would be the biggest mistake he could make. John Roberts does very well on his own."
Russell Feingold (Wisconsin)
Years on Judiciary: 10
An attorney and Roberts's classmate at Harvard Law. Independent, is often a minority of one. Is expected to push Roberts on his views on precedent. Has called for release of more documents from Roberts's time as a White House lawyer in the first Bush administration.
Quote: "Judge Roberts is unquestionably a very talented nominee, but this is a confirmation, not a coronation."
Charles Schumer (New York)
Years on Judiciary: 6
An attorney. Next to Kennedy, has been panel's most visible Democrat on Roberts's nomination. In 2001, called for moving ideology squarely into the debate over judicial confirmations. Likely to be the panel's most aggressive questioner. Led calls for the White House to release documents from Roberts's years as assistant solicitor general in first Bush administration.
Quote: "I'm making a plea: Answer the questions fully and openly."
Richard Durbin (Illinois)
Years on Judiciary: 6
An attorney. Ranks last in seniority on panel, but is No. 2 in the Senate Democratic leadership. Will be last Democrat to question Roberts - a position he says will allow him to bat cleanup. Has criticized US treatment of prisoners in Guantánamo. Often defends civil rights and the right to privacy.
Quote: "We're just not tipping our hand."
Commerce clause: Article I, Section 8 of the Constitution empowers Congress to "regulate commerce ... among the several states." Under an expansive interpretation of "commerce," Congress has passed laws ranging from civil rights guarantees to environmental protections. Conservatives say the clause permits Congress to regulate interstate commerce - nothing more.
Federalism: An approach to constitutional law that stresses the balance of federal and state powers, and that seeks to restore states' authority in the face of an expanding national government.
Judicial activism: An approach to judging in which a jurist exceeds merely rendering judgment about what the law requires and instead imposes the judge's own policy preferences.
Judicial restraint: An approach to judging that defers to the policy decisions of elected bodies unless those policies violate the Constitution.
Living Constitution: The idea that the Constitution gives judges the flexibility to issue rulings that respond to contemporary problems unforeseen or unaddressed by its 18th-century authors.
Roe v. Wade: The 1973 Supreme Court decision that established a constitutional right to abortion. Some conservatives see the ruling as an example of judicial activism.
Separation of powers: The principle that the executive, legislative, and judicial branches perform separate functions that act as a check on any one branch becoming too powerful.
Stare decisis: A principle of law in which judges abide by legal precedents established by earlier judicial rulings.
TexTualism/originalism: An approach to judging that looks to the wording of the Constitution or a statute to determine what the law requires in a particular case. Originalists look to what the precise words meant in the late 1700s when the Constitution was drafted.
Violence Against Women Act: A US law that gave women the power to sue their attackers in federal court for gender-motivated violence. In 2000, the Supreme Court ruled 5-to-4 that part of the law was unconstitutional because it exceeded Congress's authority to pass legislation under the commerce clause.