Senate Republicans, still smarting from the defeat over healthcare reform, are hinting any nomination debate could be a bare-knuckle fight. White House officials say they expect a grueling process, and only hope it doesn't drag on into election season.
Supreme Court nominees have to be confirmed by the Senate, where individual senators, even in the minority, have considerable power to delay a nomination.
Stevens, who turns 90 April 20, announced his retirement Friday. For years he has led the four-member liberal bloc on the high court and balanced it against the four-member conservative bloc, with moderate conservative Justice Anthony Kennedy often holding the swing vote.
Stevens' successor either will maintain that balance, or shift the court further to the right.
News outlets across the country have advanced the names of those believed to be on Obama's "short list" of 10 potential nominees. Some are preposterous -- like the possible nomination of U.S. Secretary of State Hillary Clinton.
But most outlets narrow the possible nominees down to three candidates, all of whom had been considered as possible successors for retiring Justice David Souter last spring before Justice Sonia Sotomayor was chosen:
Washington U.S. Appeals Court Judge Merrick B. Garland -- the only consistent male name to surface -- Chicago U.S. Appeals Court Judge Diane Wood and U.S. Solicitor General Elena Kagan.
The New York Times said Garland, well-known in the Washington legal community, would be the safest choice for Obama.
From the right, Curt Levey, director of the Washington-based Committee for Justice -- a Republican group founded to push President George W. Bush's court nominees -- told Salon there will be a hard fight unless Obama "nominates someone very moderate," like Garland.
"If (Obama) was to nominate somebody relatively moderate like a Judge Garland, I just don't think there'd be a critical mass on the right … to make for a big fight," Levey told Salon. "That's not to say there won't be criticism of the nominee, that there won't be some groups that call for the defeat of the nominee, but I just don't think you'll see a critical mass."
The Times said Wood, 59 and a divorced mother of three, is seen as the most liberal of the three front-runners. Her strong support for abortion rights would mean a confrontation with conservatives, the newspaper said.
Texas claims Wood as its own. She moved with her family from New Jersey to Houston in 1966, and is a distinguished graduate of the University of Texas and University of Texas law school, the Houston Chronicle reports. Like Garland, she was appointed to the federal bench by President Bill Clinton.
Like Kagan, she had been a professor at the University of Chicago. And also like Kagan, Obama interviewed Wood last year before nominating Sotomayor to fill his first high court vacancy.
"I got the impression that (the interview) had gone very well," Lawrence Sager, dean at University of Texas law school, told the Chronicle. "My impression is that the White House respects her a great deal."
The newspaper said allies think Wood has valuable appeals court experience sparring with powerhouse conservative judges, and the sand to stand up to conservatives on the Supreme Court.
Levey told Salon if Obama picks Wood, the fight would be "substantially bigger" than the fight over Sotomayor's nomination.
One of the Supreme Court's premier litigators and an insightful high court analyst, Washington attorney Tom Goldstein, says he thinks it will be Kagan.
Kagan, who turns 50 this month and is the youngest of the front-runners, is the first female U.S. solicitor general.
Goldstein calls Kagan, a blocked Clinton nominee for the Washington appeals court, the "prohibitive front-runner" to succeed Stevens.
"Super-smart and genuinely knowledgeable. Solicitor general. Formerly the tremendously successful dean of Harvard Law School. Personally has the greatest respect of the president, in part from their shared ties to both Chicago (she was a law professor at the University of Chicago) and Harvard. Deep relationships in the administration, particularly among those who served under Clinton. Well-known conservatives lined up around the block to support her in emphatic terms. Young! Female! Has an exceptional ability to sound extremely articulate and thoughtful without saying anything that could cause offense.
"No material track record on anything."
Stevens is the last protestant on the high court. If the Jewish Kagan succeeds him, she would join two other Jews and six Catholics on the nine-member high court, a combination that would have been unthinkable only 50 years ago.