WASHINGTON (AP (AP) -- Chief Justice John Roberts swore in Barack Obama as president Tuesday in the first of what could be many important interactions for the two men of differing politics who rose quickly to power. The encounter was briefly awkward after Obama stepped on Roberts' opening lines from the 35-word constitutionally prescribed oath of office. The chief justice wandered into a verbal detour of his own.
By tradition, the presidential oath is administered by the chief justice, and in Roberts' case, it was his first inauguration since joining the Supreme Court in 2005.
Obama used the Bible on which Abraham Lincoln took the presidential oath in 1861. Roberts concluded the oath by adding, "So help you God?" And Obama, following a practice established by George Washington and followed by most presidents, replied: "So help me God."
Other than social encounters and official events, Obama and Roberts will likely see little of each other while overseeing their branches of government. Obama's legal team could be called upon to defend the president's most important policies in front of Roberts and his conservative-leaning court.
Roberts is the youngest chief justice in more than 200 years. He easily could still be in his role a quarter century from now, long after Obama has left office.
He and Obama are similar in many ways. Both are late baby boomers - Obama is 47. And both got their law degrees from Harvard and made rapid ascents to power. But their politics diverge sharply.
Roberts was an official in Republican administrations before becoming an appeals court judge and then chief justice under Bush.
Obama was one of 22 Senate Democrats to vote against Roberts' confirmation to the Supreme Court in 2005 - the first time a Supreme Court justice has sworn in a president who voted against him.
As president, Obama will try to use any Supreme Court vacancies to counter Roberts' influence, either by replacing aging liberals with justices as young as or younger than Roberts or by changing the court's balance if a conservative justice retires unexpectedly.
The last time a chief justice swore in a president of a different party was in 1997, when Chief Justice William H. Rehnquist, a Republican, swore in Democrat Bill Clinton for a second term. Two years later, Rehnquist would preside over Clinton's impeachment trial in the Senate, which resulted in an acquittal.