Court watchers believe two of the more liberal members of the court, justices John Paul Stevens and Ruth Bader Ginsburg, could decide to step aside for reasons of age and health. That would give the president his second and third chance to shape his legacy on the Supreme Court.
Last week, when Obama took the nearly unprecedented step of criticizing the court's opinion in a major campaign finance case during his State of the Union speech, some believed he was showcasing for the American people that presidential elections, and Supreme Court nominations count.
"With all due deference to separation of powers," the president said, " last week the Supreme Court reversed a century of law that I believe will open the floodgates for special interests -- including foreign corporations -- to spend without limit in our elections. I don't think American elections should be bankrolled by America's most powerful interests, or worse, by foreign entities."
Doug Kendall, of the progressive Constitutional Accountability Center, said the president's message was clear: "President Obama's spirited reaction to Citizens United at the State of the Union indicates he fully understands the importance of the federal judiciary and the ability of the Supreme Court to stand in the way of his administration's agenda."
Kendall hopes Obama's dressing down of the majority will translate into greater attention to the judicial nomination and confirmation process.
Although five of the six justices who attended the speech sat poker faced when Obama made his comments, Justice Samuel Alito, who voted with the majority, reacted by shaking his head in irritation.
If a justice from the conservative block like Alito were to would retire, there could be a seismic shift on the court, likely giving Obama the chance to reverse the court's majority voting bloc. But speculation has centered on the liberal end of the bench.
It is widely believed that Justice Stevens, 89, sent a strong signal of his intention to retire when he confirmed for The Assoicated Press last fall that he hadn't hired a full complement of clerks for next term. The justice has been coy with the press, telling USA Today's Joan Biskupic that he was surprised by the media frenzy regarding his potential retirement.
"That can't be news" he said, declining to reveal his plans. "I'm not exactly a kid."
Justice Ginsburg, 76, announced a year ago that she had undergone surgery for early stage pancreatic cancer.
Sources close to Ginsburg dismissed retirement speculation, pointing out that she has been a lively and active participant in oral arguments this term and has on several occasions expressed an interest in serving for more years to come.
In a September press release from the court, Ginsburg revealed that she had had a "comprehensive assessment of health" last summer and that she was in "completely normal health with the exception of a low red blood cell count caused by deficiency of iron."
If one or both of the justices retire, the administration would have to calculate whether it could nominate candidates who could deliver votes as consistently liberal on major ideological issues as Stevens and Ginsburg do in an age of increasingly political confirmation wars.
"The most important thing that has changed," said Stuart Taylor of the National Journal, "is the downward spiral of partisanship in judicial nominations. It's reached a point where either party is going to make a fight on almost anyone unless the candidate is displeasing to the base of the president's party."
The administration has worked from its early days at vetting and exploring potential candidates for the court.
Those efforts intensified when Justice David Souter announced his retirement in May 2009. At the time, President Obama said that he was looking for a candidate with the "quality of empathy, of understanding and identifying with people's hopes and struggles, as an essential ingredient for arriving as just decisions and outcomes."
Top candidates went through extensive vetting before Obama settled on Justice Sonia Sotomayor. The short list then included Judge Diane Wood, Elena Kagan, Homeland Security Secretary Janet Napolitano and Michigan Gov. Jennifer Granholm.
Elena Kagan, 49, currently serves as the president's solicitor general. She is known as one of the finest constitutional scholars in the country, dazzling both liberal and conservative friends with her intellectual prowess and her ability to find consensus among ideological opposites.
Judge Diane Wood
Judge Diane Wood, 59, of the U.S. Court of Appeals for the 7th Circuit, was nominated by President Clinton in 1995. She has a wide array of job experiences away from the bench, including positions in the U.S. government at the departments of State and Justice, and as a teacher at the University of Chicago. While at the university, she played a key role in developing policies on sexual harassment and maternity leave. Unlike Kagan, Wood has had to wrestle with hot-button issues such as abortion. Potential confirmation hearings would be lively and controversial.
Homeland Security Secretary Janet Napolitano, 52, enjoys a close relationship with the president and would be an "outside the judicial box" candidate, but may be roundly criticized for her comments after the arrest of Umar Farouk Abdulmuttalab, who attempted to bring down a Northwest Airlines flight with explosives. Napolitano initially told ABC News, "Once the incident occurred, the system worked." A day later, she had a slightly different message on NBC News: "Our system did not work in this instance," she said. President Obama later ordered an extensive review.
Other Possible Candidates
Others, such as Leah Ward Sears, former chief of the Georgia Supreme Court , are also on potential short lists, but those lists can shift.
"Short lists probably don't change too much from vacancy to vacancy, but rankings within the short list probably fluctuate based on who's being replaced, Kendall said.
he noted that, unlike the previous vacancy, the next one could be filled by a male.
Many believe that Obama could turn to Judge Merrick Garland, 58, a graduate of Harvard Law School and former law clerk for Supreme Court Justice William Brennan, Jr. He currently sits on the U.S. Court of Appeals for District of Columbia Circuit.
Another possibility is Cass Sunstein, 55, a close confident of the president who currently heads the White House Office of Information and Regulatory Affairs.