Chief Justice nominee John G. Roberts Jr. won the Senate Judiciary Committee's endorsement yesterday with unanimous Republican support and the backing of three Democrats who said they hope he will keep his promise not to be an ideologue.

The 13 to 5 vote reflected Roberts's praised performance at last week's hearing and the Democrats' inability or unwillingness to mount a united campaign against him. While Republicans and Democrats agreed President Bush's next Supreme Court nomination will be far more contentious, liberal activists clearly saw yesterday's vote for the conservative Roberts as a blow to their effort to maintain a voice in shaping the judiciary.

Roberts, 50, would replace the late William H. Rehnquist, a reliable conservative vote on the high court. Perhaps as early as next week, Bush will nominate a replacement for retiring Justice Sandra Day O'Connor, a centrist. Her successor could play a major role in pushing the court to the left or right.

The soothing tones and anticlimactic windup of Roberts's confirmation are unlikely to be repeated in the looming battle to replace O'Connor, an array of lawmakers and activists said. "It's Armageddon," said Sen. Orrin G. Hatch (R-Utah), a Judiciary Committee member who strongly backed Roberts.

The full Senate plans to vote on Roberts's nomination next week, when he is all but assured of being confirmed as the nation's 17th chief justice. White House spokesman Scott McClellan said Roberts "is going to make an outstanding chief justice."

The three committee Democrats who voted for Roberts -- Russell Feingold and Herbert Kohl of Wisconsin and Patrick J. Leahy of Vermont -- have liberal voting records, and their votes dismayed many groups important to the party's base. A number of Democratic senators from Republican-leaning states have said they will support Roberts next week, leaving their party split almost down the middle on the first Supreme Court opening in 11 years. "I will vote my hopes today and not my fears," Kohl said.

With the committee vote over, other Democrats began to line up for and against Roberts. Hillary Rodham Clinton (N.Y.), announced yesterday that she will vote no on the nomination, as did Barack Obama (Ill.). Robert Byrd (W.Va.) and Mark Pryor (Ark.) said they will vote to approve Roberts.

"Today was a defeat, there's no question about that," said Ralph G. Neas of the liberal People for the American Way.

Nan Aron of the Alliance for Justice called the committee vote "deeply disappointing." But, she added, "We expect the next nomination to ignite a firestorm of opposition. . . . We've just begun to fight."

Roberts's supporters praised his intellect, knowledge and cautious answers that avoided suggesting how he might vote on issues that could come before the court. The five Democrats who opposed him said he dodged too many questions, and they faulted the Bush administration for refusing to provide documents from Roberts's highest-ranking job in government: deputy solicitor general.

All they were left with, they said, were memos that Roberts wrote as a government lawyer in the 1980s, when he questioned, among other things, the "so-called right to privacy." A woman's right to privacy is the legal underpinning for the landmark Roe v. Wade abortion ruling.

"I knew as little about what Judge Roberts really thought after the hearings as I did before the hearings," said Sen. Dianne Feinstein (D-Calif.) who voted against him. She told reporters that she agonized over the decision, calling fellow committee member Charles E. Schumer (D-N.Y.) late Wednesday, and almost phoning Roberts last weekend.

Republican and Democratic senators presented sharply different conceptions of the proper standard for elevating a judge to the Supreme Court. Sen. Edward M. Kennedy (D-Mass.), who voted against confirmation, said the central issue was whether Roberts is committed to civil rights. "Nominees must earn their confirmation by providing us with full knowledge of their values and convictions they'll bring to decisions that may profoundly affect our progress as a nation toward the ideal of equality," Kennedy said. "Judge Roberts has not done so."

Republicans countered that senators should not explore a nominee's philosophical views. Sen. Lindsey O. Graham (R-S.C.) said: "If we could look at the person before us based on qualifications, character and integrity, and not require them to show an allegiance to a particular case or a cause, it would serve the country well."

Senators in both parties emphasized the gravity of their votes, noting that Roberts could lead the court for decades. "He will have more impact on our lives, in the future of our children's lives, than any of us and all of us combined," said Sen. Joseph R. Biden Jr. (D-Del.), who cast a negative vote.

Even as the committee was finishing with Roberts, anxiety over the next nomination was palpable in the hearing room.

Committee Chairman Arlen Specter (R-Pa.) said he had told Bush this week to expect the next nominee's confirmation hearings to be "very contentious," because -- with the balance of the court at stake -- senators will be even more eager to learn views that the candidate inevitably will refuse to divulge. "It's going to produce a lot of angst," Specter said.

Leahy, the panel's ranking Democrat, chastised the president for not being more open to a true exchange of views.

"I hope that this time the president will follow through, share with us his intentions, and even seek our advice before he acts; that little thing called the advice-and-consent clause of the Constitution," Leahy said.

Schumer said in an interview that Democrats made independent decisions about Roberts, while Republicans "are marching in lockstep." Still, he said, "We're walking away from this in a very good place to prepare for the next battle."

A Senate panel approved Roberts yesterday.