Obama is expected to announce his nominee this week, as early as Tuesday. His words, his young presidency and his own life experience reveal what Americans should expect - and help explain how the president is making a decision that will endure long after he leaves office.
"You have to have not only the intellect to be able to effectively apply the law to cases before you," Obama said in an interview carried Saturday on C-SPAN television. "But you have to be able to stand in somebody else's shoes and see through their eyes and get a sense of how the law might work or not work in practical day-to-day living."
That quality - Obama calls it empathy - is a huge factor in picking a successor to retiring Justice David Souter. Among the others Obama is weighing: judicial philosophy, intellectual sway, gender, ethnicity, age and the politics of Senate confirmation.
He is expected to choose a woman, and perhaps someone who is Hispanic, but insists he will not be "weighed down" by demographics.
Ultimately, it may come down to an intangible - how well the nominee resonates with Obama. A president's tenure will last at most eight years, but his choice of a Supreme Court nominee could affect the course of the United States for a generation, and his personal legacy for even longer.
Souter is part of the court's four-member liberal wing, and his replacement by Obama probably won't change the court's ideological balance. There are four predictably conservative judges, and right-of-center Justice Anthony Kennedy, in the middle, is in effect the deciding vote.
The six people known to be under consideration by Obama are U.S. Appeals Court judges Sonia Sotomayor and Diane Wood, Solicitor General Elena Kagan, Michigan Gov. Jennifer Granholm, Homeland Security Secretary Janet Napolitano and California Supreme Court Justice Carlos Moreno.
It remains possible that Obama could nominate someone else who would surprise the legal, political and media communities tracking his deliberations.
His approach, though, is methodical.
He consulted senators on the Judiciary Committee, without revealing much. His aides gave an audience to interest groups, but warned them that Obama did not want to be lobbied. Obama is conferring with a circle of advisers, but is heavily involved in his own review as a lawyer who loves constitutional law.
"He makes the decision himself, but I think he welcomes arguments and counter-arguments from other people," said David Strauss, a professor at the University of Chicago's law school who knows Obama from when they both taught there. "He wants to hear, `What are the problems with going this route?' "
Obama says he wants to give the Senate a traditional 70 days to confirm his nominee - which, by the calendar, means he plans to announce a pick this week.
Tucked away with family at the Camp David presidential retreat in Maryland for most of the holiday weekend, Obama has not made a decision yet, aides say.
Here is what he is weighing:
"Having a giant on the bench - somebody who has the personality to help drive the decisions - I think that's valuable," said Bill Marshall, a law professor at the University of North Carolina at Chapel Hill who worked in President Bill Clinton's White House. "I think (Obama) gets that from being a constitutional law professor. He knows about the importance of those interpersonal skills."
By BEN FELLER