President Barack Obama on Tuesday nominated a Hispanic judge, Sonia Sotomayor, to the US Supreme Court - a choice unlikely to shift the ideological balance on the country's highest judicial panel. Obama's selection of the 54-year-old Sotomayor, whose parents moved to New York City from Puerto Rico before her birth, is an exercise of one of the most significant powers the US Constitution grants the American chief executive. The president said he selected Sotomayor based on his search for a candidate with a "rigorous intellect" and "a mastery of the law" and one who recognized "the limits of the judicial role." Sotomayor said "my heart today is bursting with gratitude" and called the nomination the "most humbling honor of my life." Before selecting the nominee, Obama had said he was looking for a prospective high court justice who would bring "empathy" to the bench, a judge capable of understanding the effects of high court rulings on the lives of Americans. Standing next of Obama in the White House East Room, Sotomayor echoed that point: "I strive never to forget the real world consequences of my decisions." If confirmed by the Senate, she would succeed retiring Justice David Souter, one of four reliably liberal votes on the nine-member court, and would be expected to vote with the liberal bloc. There are four equally dependable conservative votes, leaving Justice Anthony Kennedy, a centrist, to cast the deciding ballot when the other members split 4-4. Regardless, Sotomayor would inject relative youth into the court's aging liberal wing. Justices serve until they retire or die, giving presidents an opportunity to influence policy long after they leave office. Obama's nomination is the first by a Democratic president in 15 years. She would join Justice Ruth Bader Ginsburg as the second woman on the current court, the third in history. Former Justice Sandra Day O'Connor was the first woman on the Supreme Court. Obama's Democrats are just one Senate vote shy of the 60 necessary to prevent a Republican filibuster, a tactic designed to delay or defeat a proposal. But going into the confirmation process an outright Republican attempt to block Sotomayor appeared unlikely. Any decision to filibuster could carry deep political risks - Hispanics are the fastest-growing segment of the population and an increasingly important one politically. Still, Republicans could try to use her nomination to galvanize the party base. Obama's announcement leaves the Senate four months - more than enough time by traditional standards - to complete confirmation proceedings before the Court begins its next term in the fall. As a judge, Sotomayor has a bipartisan pedigree. She was first appointed to the federal bench by a Republican, President George H.W. Bush, then named an appeals judge by Democratic President Bill Clinton in 1997. At her Senate confirmation hearing more than a decade ago, she said, "I don't believe we should bend the Constitution under any circumstance. It says what it says. We should do honor to it." Such statements could provide solace to conservative Republicans who often argue that liberal judges seek to legislate from the bench by imposing their own political philosophy to interpretation of the Constitution. Abortion rights have been a flashpoint in several recent Supreme Court confirmations, although Sotomayor has not authored any controversial rulings on the subject. There is the possibility that Obama, before his four-year term is out, may be given the opportunity for more appointments, allowing him to reshape the court that has, in recent years, moved to the right with President George W. Bush's choice of conservative Justice Samuel Alito Jr. to replace the moderate O'Connor.