by David Weisbrot
The recent resignation of Justice John Paul Stevens, the most senior figure on the United States Supreme Court, paves the way for the second Supreme Court nomination in as many years for the Obama administration.
Not surprisingly, since the inauguration, liberal commentators have been fantasising about the day that President Barack Obama can make sufficient new appointments to the Supreme Court to shift the balance of power away from what is now a conservative core of judges.
So what will be in store for the court now that Stevens, is stepping down?
Justice Stevens was appointed by Republican President Gerald Ford in 1975. At the time he was considered a moderate conservative, but in the ensuing years he has come to be seen as a mainstay of the liberal wing of the court.
Stevens, who turns 90 this month, claims his views haven't changed; rather it's the society around him that has shifted to the right. Either way, his replacement is unlikely to fundamentally alter the existing balance of power on the court.
Nevertheless, every appointment to the highest court in the US is heavily scrutinised and increasingly politicised, so who will Obama likely nominate for this vacancy?
Six months ago the Senate confirmed the President's first nominee, Sonia Sotomayor. She was in many ways the perfect candidate for Obama, offering the chance to appoint the first person of Hispanic heritage (and only the third woman) to the Supreme Court, in a country with a large and increasingly influential Hispanic population.
Sotomayor's personal story also appealed to Obama: from a humble background, she struggled with childhood diabetes, yet achieved brilliant academic results at elite institutions (Princeton and Yale School).
She is regarded as a judicial moderate with a solid record, and she personified the bipartisan spirit that Obama pledged to pursue, having first been appointed to the bench by President George H.W. Bush.
Nevertheless, there were 31 votes against her nomination (all but nine of the Republican senators), despite her qualifications and experience, her generally moderate stance, her previous nomination by a Republican administration, and the fact that many Republicans were concerned about alienating Hispanic voters.
The president interviewed three other candidates last year before settling on Sotomayor.
Justice Diane Wood is a distinguished federal appeals court judge, who like President Obama once taught law at the University of Chicago.
Elena Kagan is now the US Solicitor-General, and is another former professor at Chicago and Dean of Harvard Law School.
Janet Napolitano is now Secretary for Homeland Security.
Wood and Kagan are thought to be among the strongest contenders this time around.
Other known Obama favourites include Harold Hongju Koh, formerly Dean of Yale Law School and a leading expert on international human rights law.
A Korean-American, Koh provides Obama with the opportunity to appoint the first Asian-American to the Supreme Court. Koh is the most liberal of the potential nominees and was highly critical of the Bush administration's record on civil liberties.
Koh also favours the consideration by American courts, in certain circumstances, of international law - something anathema to Justice Scalia and other judicial conservatives.
Koh is now the top legal adviser to the US State Department. His confirmation was long delayed by Republican senators, although five moderates ultimately supported him.
Merrick Garland is a Justice of the US Court of Appeals (DC Circuit), and also has the classic profile for a Supreme Court nominee: he graduated from and later taught at Harvard Law School, and worked for one of the most powerful Washington law firms, Arnold and Porter.
He also served as a federal prosecutor, including in such high-profile cases as the Oklahoma City bombing and the Unabomber trials.
Conservative lobbyists have already flagged Garland as the nominee that Republicans would be most likely to support.
Some commentators have lamented the absence, since the retirement of Sandra Day Connor in 2006, of judges with senior political experience, who can bring a pragmatic perspective on the day-to-day exigencies of government.
Two potential candidates fill this bill, although neither has judicial experience: Deval Patrick, the first African-American Governor of Massachusetts, a friend of President Obama and a senior lawyer in the Clinton administration. Michigan Governor Jennifer Granholm is highly regarded, a former state attorney-general, and a member of Obamas transition team.
The cheekiest suggestion so far comes from US law professor Jeffrey Rosen, who recently argued in the Washington Post that the cool and analytical President Obama is temperamentally more suited to being a Supreme Court justice than being a deal-brokering politician so he should nominate himself when the next vacancy occurs!
I thought Sonia Sotomayor was the clearly compelling candidate last year, for the reasons mentioned. I suspect that, in his heart, President Obama would love to make another striking appointment in this vein, but will he risk a bruising and fraught nomination process?
Koh's strongly liberal views might make him a difficult sell to the Senate, but he is a brilliant lawyer and offers Obama the opportunity for another historic first.
Justice Wood was on the cusp last time, and would play well to Obama's Democratic base, but Republican Senators would no doubt seek to pick apart her liberal record on the bench.
Kagan is another outstanding legal mind, her roots are in the same Chicago-Harvard axis as the President, and at 49 would have a long future on the court. As Solicitor-General, she has a moderate record, and to the consternation of liberals has often defended the actions of the previous Bush administration in the courts.
With the recent loss of the Senate seat in Massachusetts, Obama no longer has a filibuster-proof majority in the Senate, so he may be inclined to be cautious, especially if he wants to lower the temperature after the heated and highly partisan healthcare debate, in the run-up to the important mid-term elections in November.
Koh would be the gutsiest choice, and the one to connect with Obama supporters who voted for "change we can believe in". Wood may be the most faithful replacement for Justice Stevens in terms of judicial approach. Kagan and, especially, Garland are the safer choices in terms of gaining confirmation.
The big test is still to come, when the balance of power on the court is in play. However, with a choice of excellent candidates across the Democratic spectrum, this nomination should tell us a great deal about President Obama's own judicial philosophy.
David Weisbrot is Professor of Legal Policy at the United States Studies Centre and Professor of Law and Governance at Macquarie University.