Sept. 29 (Bloomberg) -- John G. Roberts Jr. was sworn in as the 17th U.S. chief justice today, replacing the man for whom he once worked and becoming the first new member of the Supreme Court in 11 years.

With tears welling up in his eyes, Roberts paid tribute to his predecessor, the late William H. Rehnquist, as he took the oath at a White House ceremony just hours after his bipartisan confirmation by the Senate. Rehnquist's death on Sept. 3 at age 80 prompted President George W. Bush to renominate Roberts to lead the court. Roberts was originally in line to replace Justice Sandra Day O'Connor after she announced her retirement in July.

The Senate's endorsement is ``confirmation of what is for me a bedrock principle, that judging is different than politics,'' Roberts said. ``Every generation in its turn must accept the responsibility of supporting and defending the Constitution and bearing true faith and allegiance to it.''

Roberts, 50, now the youngest member of the high court, took the oath of office from the oldest, Justice John Paul Stevens, 85. Rehnquist, who hired Roberts as a clerk for the court's 1980-81 term, served as chief justice for 19 years.

Bush, in the East Room of the White House, lauded Roberts as a man of ``integrity, deep humility and uncommon talent'' who will be ``a faithful guardian of the Constitution.''

Senate Confirmation

The Senate voted 78-22 to confirm Roberts, with united Republicans and half the Democrats supporting the former federal appeals court judge.

Roberts will preside over the Supreme Court as it convenes its new term Oct. 3. He will take part in a formal investiture ceremony and take a second oath in the courtroom before the justices begin hearing arguments.

Even before today's swearing-in, attention turned to a possible battle over replacing O'Connor. At least one Democrat warned of a filibuster if Bush chooses someone regarded by opponents as too extreme.

While Bush is close to naming a successor to O'Connor, White House spokesman Scott McClellan said the announcement wouldn't come today. The list of candidates ``is not that long'' and Bush is ``essentially wrapping up'' the process and the announcement could come at any time, McClellan said.

O'Connor, the first woman on the Supreme Court, has agreed to stay on until her replacement is confirmed.

Roberts ``has demonstrated he won't let personal opinions sway his fair-minded approach,'' said Senate Majority Leader Bill Frist. ``He will check political views at the door of the court.''

Three-Month Process

Today's Senate vote capped a three-month process for Roberts that began when Bush nominated him to succeed O'Connor.

As the Senate roll call was taken, Roberts was at the White House with Bush and about 30 others in the Roosevelt Room. The group erupted in applause when the tally reached a majority of 51, McClellan told reporters.

Then ``someone reminded them that the gavel had not come down and it wasn't official,'' McClellan said. Roberts's wife Jane watched the proceedings from the Senate spectator gallery and then headed to the White House to join her husband, Bush and first lady Laura Bush for lunch.

As for O'Connor's seat, Democrats urged Bush to nominate a moderate to avoid a Senate fight. O'Connor has often been the decisive vote on such issues as abortion and affirmative action.

``I urged the president to live up to his original promise to be a uniter, not a divider,'' said Senator Patrick Leahy, a Vermont Democrat who split with his party's leader to vote for Roberts.

Possible Filibuster

Senator Charles E. Schumer of New York said he and fellow Democrats would be prepared to use a filibuster, a tactic that permits unlimited debate, to block someone viewed as a conservative ``ideologue.''

Ohio Republican Mike DeWine, who helped avert a showdown over the filibuster issue in May, predicted centrist Democrats will head off the use of the delaying tactic.

``I don't think the American people want to see a filibuster,'' he said.

While Bush is close to naming a successor to O'Connor, McClellan said the announcement wouldn't come today. The list of candidates ``is not that long'' and Bush is ``essentially wrapping up'' the process and the announcement could come at any time, he said.

O'Connor, the first woman on the Supreme Court, has agreed to stay on until her replacement is confirmed.

Abortion Rights

Democrats who voted for Roberts said Judiciary Committee testimony led them to conclude that he wouldn't overturn the 1973 Supreme Court decision that legalized abortion because he endorsed a right of privacy in the Constitution that underpinned the abortion rights ruling. He said the court's abortion decisions were precedents deserving respect.

These lawmakers also pointed to Roberts's statement that ``I'm not an ideologue'' as well as testimony they said indicated he wouldn't join conservative Justices Clarence Thomas and Antonin Scalia in voting to limit the power of Congress.

Roberts's support spanned the Democrats' ideological spectrum, including several senators from states that went Democratic in the 2004 presidential election. They include Carl Levin of Michigan, Christopher Dodd of Connecticut, Patty Murray of Washington, Russ Feingold and Herb Kohl, both of Wisconsin, Tom Carper of Delaware and Joseph Lieberman of Connecticut, who ran for vice president in 2000.

Democrats from states that Bush carried in 2004 are prominent among Roberts's supporters. They include Ben Nelson of Nebraska, Bill Nelson of Florida, Ken Salazar of Colorado, Jeff Bingaman of New Mexico, Tim Johnson of South Dakota, and North Dakota's two senators, Kent Conrad and Byron Dorgan.

Other Democrats from so-called red states backing Roberts are Mary Landrieu of Louisiana, Blanche Lincoln and Mark Pryor of Arkansas, Max Baucus of Montana, and Robert Byrd and Jay Rockefeller of West Virginia.

Protecting Rights

Senate Democratic leader Harry Reid of Nevada voted against Roberts because he hadn't ``persuaded us he will protect the freedoms that all Americans hold dear.''

Those mentioned as possible successors to O'Connor include PepsiCo Inc. General Counsel Larry D. Thompson, a former deputy attorney general; Michigan Supreme Court Justice Maura D. Corrigan; Alice Batchelder, a judge in the Cincinnati-based 6th U.S. Circuit Court of Appeals; Priscilla Owen, confirmed last May to the New Orleans-based 5th U.S. Circuit Court of Appeals; White House Counsel Harriet Miers; Attorney General Alberto Gonzales; and appeals court judges J. Michael Luttig of the 4th U.S. Circuit Court of Appeals in Richmond and Samuel Alito of the 3rd Circuit in Philadelphia.

Owen was among 10 appellate court nominees Democrats blocked during Bush's first term by using the filibuster, a tactic that permits unlimited debate. Owen was confirmed following a deal that averted a showdown over a Republican plan to eliminate the filibuster against judicial nominees.

Schumer said Bush could expect a fight if he nominated Owen or Janice Rogers Brown, another of the filibustered nominees who won confirmation in June to the same court on which Roberts serves.

To contact the reporter on this story: Holly Rosenkrantz in Washington at hrosenkrantz@bloomberg.net

Last Updated: September 29, 2005 16:23 EDT