Roberts, at 50, becomes the 17th chief justice, presiding over a Supreme Court that seems as divided as the nation over abortion and other tumultuous social issues. The court opens a new term on Monday.
"The Senate has confirmed a man with an astute mind and kind heart," President Bush said just before Roberts was sworn in by acting Chief Justice John Paul Stevens. "All Americans can be confident that the 17th chief justice of the United States will be prudent in exercising judicial power, firm in defending judicial independence and above all a faithful guardian of the Constitution."
Mr. Bush is expected to make his second Supreme Court nomination within days, one that conservatives hope will move the court to the right. Replacing Rehnquist with Roberts keeps the court's current balance, but replacing the moderate Justice Sandra Day O'Connor with a conservative could tilt it rightward.
Roberts called the Senate's 78-22 bipartisan vote for him "confirmation of what is for me a bedrock principle, that judging is different from politics." All of the Senate's 55 Republicans, independent James Jeffords of Vermont and half of the 44 Democrats supported him.
CBS News chief White House correspondent John Roberts reports that the mood at Roberts' swearing in was, at times,
"We extend a special welcome to his wife Jane, their daughter Josie and son Jack," Mr. Bush said. "A fellow who is comfortable with the cameras."
But on a more serious note, the conservative chief justice said he will remain faithful to the constitution.
He said he would try to "pass on to my children's generation a charter of self-government as strong and as vibrant as the one that Chief Justice Rehnquist passed on to us."
"What Daniel Webster termed the miracle of our Constitution is not something that happens in every generation, but every generation in its turn must accept the responsibility of supporting and defending the Constitution and bearing true faith and allegiance to it," Roberts said.
A crowd including seven of the eight sitting justices, Roberts' parents, Rosemary and John Sr., Senate supporters and White House well-wishers erupted stood and applauded as Roberts kissed his wife and shook Stevens' hand. The audience also included Attorney General Alberto Gonzales and White House counsel Harriet Miers, both of whom have been mentioned as candidates for O'Connor's seat.