Washington (CNN) -- Justice John Paul Stevens is expected to announce by month's end whether he will retire from the Supreme Court, sources close to him tell CNN. His departure after nearly 35 years on the bench would give President Obama another opportunity to shape the nation's highest court.
Stevens, who turns 90 on April 20, has told colleagues he wants to decide soon -- for his own peace of mind -- but also to give the White House time to select a replacement and for the Senate to confirm the nominee.
He was not on the bench for a brief public session Monday; the court will hold its next public session in two weeks.
Sources close to him suggest he could announce something during this two-week recess, or shortly after the high court's oral arguments end for the term April 28. As of late last month, Stevens had not formally made up his mind, the sources said.
Those sources asked not to be identified because they are not authorized to speak for Stevens, who himself has only hinted at his future.
CNN Senior Legal Analyst Jeffrey Toobin, who interviewed the media-shy justice in early March, is convinced he will leave the court this year. "The fact that he's given interviews to me and others, which is also very out of character for him, suggests that this is part of a leave-taking operation," Toobin said.
But several close friends suggest Stevens may wish to stay for another year, and several former law clerks have privately encouraged him to do just that.
Sen. Arlen Specter, D-Pennsylvania, a member of the Judiciary Committee that would hold confirmation hearings for any replacement, urged Stevens to delay his exit.
"I think the gridlock in the Senate might well produce a filibuster, which would tie up the Senate on a Supreme Court nominee," Specter told Fox News Sunday. "I think if a year passes, there's a much better chance we can come to a consensus."
Speculation over Stevens has increased since he confirmed last fall he had hired only one law clerk for the next court term, which begins in October. Sitting justices can hire four law clerks, while retired members only get one.
The White House has quietly but actively prepared for weeks in anticipation of a vacancy, government sources told CNN. Top officials have no specific information that Stevens or even another justice will retire after the court's session ends in late June, but want to be ready, those sources emphasized.
Obama nominated Justice Sonia Sotomayor last year, putting the first Hispanic on the court. Democrats cited that choice as a uniting force among progressives, saying it gave the president a signature moment in his first year in office. White House officials privately express hope another high-profile nomination would build political momentum in an election year.
"There isn't an immediate candidate who could give them just as much the second go-around," said Thomas Goldstein, a prominent Washington lawyer and founder of Scotusblog online. "There isn't a candidate who has Justice Sotomayor's personal history and also her ethnic background. But I think that the model for the administration is probably the same -- get someone in there who doesn't generate a lot of political heat against you and is a relatively easy person to confirm."
Some Senate Republicans certainly hope that will be the strategy.
"I think the president will nominate a qualified person. I hope, however, he does not nominate an overly ideological person," said Sen. Jon Kyl, R-Arizona, another member of the Judiciary Committee, told Fox News on Sunday. "That will be the test. And if he doesn't nominate someone who is overly ideological, you may see Republicans vote against the nominee, but you won't see them engage in a filibuster."
Government sources say three candidates top the current, informal list of possibles at this very early stage:
• Judge Diane Wood, 59, of the Illinois-based 7th Circuit U.S. Court of Appeals. Many administration insiders believe this Texas native would be a strong intellectual force on the high court, where the newly emboldened conservative justices have achieved recent victories on campaign finance reform and gun rights.
• Solicitor General Elena Kagan, 49, who has no judicial experience but has impressed the White House with her skill arguing a range of important cases before the Supreme Court as the government's top appellate attorney.
• Judge Merrick Garland, of the U.S. Court of Appeals for the D.C. Circuit. The 57-year-old Chicago, Illinois, native is considered more moderate than other leading candidates, and his confirmation could be considered a relative breeze.
All three were among nine finalists last year for the seat that went to Sotomayor, said sources with knowledge of the process. She, Wood and Kagan were personally interviewed for the job by the president, they said. Homeland Security Secretary Janet Napolitano also met privately with Obama last May, and remains in the mix, sources said.
Other possible contenders could be Cass Sunstein, 55, an old law school associate of Obama and head of a key White House agency; and Massachusetts Gov. Deval Patrick, 53, a longtime friend of the president. Patrick is favored by some insiders but is seeking re-election this fall to his current job.
It took about 26 days for Obama to announce his selection of Sotomayor, but officials hint the president may be prepared to move much faster if Stevens steps aside.
Cynthia Hogan, Vice President Joe Biden's chief counsel, headed the day-to-day vetting and confirmation process for Sotomayor, and government sources say she would be likely to play the lead role again. Obama's new White House counsel, Bob Bauer, also would be likely to serve a key liaison role, given his long political experience working as an adviser to several Democratic lawmakers.
One source said if Stevens were to retire, there would be less political pressure on Obama to name another woman to the court. Justice David Souter's exit led to universal agreement inside the White House that a woman should join Justice Ruth Bader Ginsburg, then the lone female on the court.
Many advocacy groups believe there will be a high court vacancy this year, and have already sounded the alarm on the political and social stakes.
"If in fact Justice Stevens is stepping down, he's been a major strategist and tactician on the court," said Nan Aron, president of the left-leaning Alliance for Justice. "The president should start putting together a list of names of individuals who can begin to change the conversation on the court and assert a leadership role."
Aron cited Wood as someone with a long record of taking strong stands on a variety of key issues.
On the right, many observers seem confident that in an election year filled with several legislative challenges, Obama could have a hard time choosing a high court nominee with a clear liberal portfolio.
"The burden of proof is clearly on the White House with any future Supreme Court nominations," said Gary Marx, executive director of the Virginia-based Judicial Crisis Network. "It was assumed on the last go-around that it would be more of a rubber stamp," with Sotomayor winning easy confirmation. "But we're in an entirely new world politically. Obama, I think, wants to take a more aggressive posture, and continue to appeal to his liberal base with the next court nominee, but the Democratic Senate may decide it's not in their best interest to hitch their wagon to the president."
One legal source who was deeply involved in the vetting process for Sotomayor cautioned against Obama picking what was termed a "liberal [Antonin] Scalia," saying, "it could derail the president's entire agenda, by picking a fight over ideology. Very much in line with his philosophy of picking qualified, thoughtful judges, the president was extremely successful naming Judge Sotomayor last year. I'd expect him to follow that same path if we get something this year."
One sign of encouragement for Democrats was the president's strong tone dressing down high court conservatives in his recent State of the Union address. Obama criticized the majority's ruling giving corporations greater power to spend their money in federal elections, causing Justice Samuel Alito, sitting in the audience, to shake his head and mouth words interpreted as "not true."