John Glover Roberts Jr. was sworn in yesterday as the 17th chief justice of the United States, enabling President Bush to put his stamp on the Supreme Court for decades to come, even as he prepares to name a second nominee to the nine-member court.

The White House swearing-in ceremony took place three hours after the Senate voted 78 to 22 to confirm Roberts. All 55 Republicans, half the 44 Democrats and independent Sen. James M. Jeffords (Vt.) voted yes.

The vote reflected the gap between many Senate Democrats and the liberal groups that strongly opposed Roberts and are important to the party's base. Senators in both parties predicted a much more bruising fight over Bush's upcoming choice to succeed centrist Sandra Day O'Connor. Liberal activists said they will expect more spirited opposition from rank-and-file Democrats, but some Republicans said the relative ease of Roberts's confirmation suggests that opponents will find it extremely difficult to block anyone picked by Bush.

When the Supreme Court opens its new session Monday, Roberts, 50, will take the court's center seat that his mentor, the late William H. Rehnquist, occupied for 19 years. "The Senate has confirmed a man with an astute mind and a kind heart," Bush said at the swearing-in. Roberts "will be prudent in exercising judicial power, firm in defending judicial independence and, above all, a faithful guardian of the Constitution," the president added.

The Senate Democrats' 22 to 22 split illuminated the influence that presidential politics and red-state, blue-state considerations play in a party struggling to end nearly a decade of unbroken GOP control of Congress. Among those opposing Roberts were presidential aspirants who typically veer to the center but now are eyeing the liberal activist groups that will play key roles in Iowa, New Hampshire and other early-voting states in 2008. They included Sens. Evan Bayh (Ind.), Joseph R. Biden Jr. (Del.) and Hillary Rodham Clinton (N.Y.). Also voting no were two senators facing potentially tough reelections next year in states with powerful left-leaning groups: Maria Cantwell of Washington and Debbie Stabenow of Michigan. Maryland's Democratic senators voted against Roberts.

Democrats voting for Roberts included several facing reelection contests next year in states that Bush carried twice: Ben Nelson of Nebraska, Bill Nelson of Florida, Robert C. Byrd of West Virginia and Kent Conrad of North Dakota. These and other red-state Democrats who backed Roberts pose the biggest challenge to liberals hoping for a united party front if Bush nominates a staunch conservative next.

Those activists took some comfort yesterday in the belief that Roberts's conservatism will be similar to Rehnquist's and that therefore the court will change little politically. The stakes are far higher for the next pick, they said, because O'Connor has provided the swing vote on many 5 to 4 decisions. O'Connor will remain on the court until her successor is confirmed.

"The pivotal appointment is the next one," said Sen. Dianne Feinstein (D-Calif.), who opposed Roberts. "The comparison obviously is with O'Connor," she said, in contrast to the reliably conservative Rehnquist. Asked how much she feared that Bush will name someone more conservative than Roberts, she replied: "Very. On a scale of one to 10? Eight and a half."

Republicans said the next nominee should be held to no higher standard than was Roberts, suggesting that the new chief justice has blazed a path others can follow. "Every single judicial nominee deserves to be considered on his or her own merits and not juxtaposed with their predecessors or horse-traded for ideological reasons," said Sen. Jon Kyl (R-Ariz.).

Bush is poised to announce his next nomination within days, administration officials and GOP strategists say. With Wednesday's indictment of former House majority leader Tom DeLay (R-Tex.) creating unwanted headlines, some Republican advisers urged an announcement today, but sources said that idea was rejected.

Among Republicans close to the White House, the most commonly mentioned candidates in the past couple of days were White House counsel Harriet Miers, former deputy attorney general Larry D. Thompson and Judge Karen J. Williams of the U.S. Court of Appeals for the 4th Circuit. Miers, a late addition to the public list, is close to Bush from their Texas days when she was his personal lawyer. Thompson, who is black, is a Bush favorite from the first term. And Williams has impressed many Bush advisers as a strong potential choice.

Also mentioned were appellate judges Alice M. Batchelder of the 6th Circuit and Priscilla R. Owen of the D.C. Circuit, as well as Maura D. Corrigan of the Michigan Supreme Court. If Bush does not opt for a woman or a minority, the leading white male candidates appear to be J. Michael Luttig of the 4th Circuit and Samuel A. Alito Jr. of the 3rd Circuit. Some former Bush aides think he may pick his friend Attorney General Alberto R. Gonzales, but other Republicans said they think conservative opposition has undermined him too much for him to be chosen.

Owen would almost surely trigger fierce opposition, because Senate Democrats blocked her appellate court nomination with a filibuster in Bush's first term. Owen and several other filibustered nominees were eventually confirmed only after a May compromise that ended a Republican threat to outlaw judicial filibusters.

Democrats would see Owen's nomination as essentially an insult, party sources said. "If it's an ideologue such as a Janice Rogers Brown or an Owen," said Sen. Charles E. Schumer (D-N.Y.), mentioning another once-filibustered judge, "I think there's a good chance that we would move to block it on the floor" with unending debate.

Numerous Republicans have said an effort to filibuster a Supreme Court nominee chosen by a twice-elected president would be foolhardy. If necessary, some said, Republicans would revive their plan to change Senate rules and bar judicial filibusters.

Roberts, who was a lawyer in the Reagan and George H.W. Bush administrations and later an appellate judge, drew rave reviews from many senators for his encyclopedic knowledge of constitutional law and his smooth answers during two days of Senate hearings this month. Liberals complained that he dodged too many questions, including those meant to reveal his beliefs about abortion and other contentious issues.

"I am not an ideologue," Roberts said at the hearings. He underlined the point yesterday in his brief White House speech after Justice John Paul Stevens, the most senior member of the court, administered the oath of office. "Judging is different from politics," Roberts said as his wife, Jane, their two children, the president and dozens of administration supporters looked on.

Roberts also said he hoped to "pass on to my children's generation a charter of self-government as strong and as vibrant" as the one Rehnquist left for his.

For an administration plagued by high gasoline prices, bad reviews for hurricane response and ethics problems for key congressional allies, Roberts's almost flawless confirmation process was a welcome success. "I think history will say that George W. Bush knocked it out of the park when he selected John Roberts to be chief justice of the United States," Sen. Lindsey O. Graham (R-S.C.) told reporters.

Staff writer Michael A. Fletcher contributed to this report.

Shortly after his swearing-in, Chief Justice John G. Roberts Jr. is welcomed to the East Wing of the White House by supporters, including Vice President Cheney, left, and President Bush.John G. Roberts Jr., with wife Jane, is sworn in by Justice John Paul Stevens. Roberts will be "a faithful guardian of the Constitution," President Bush said.