In the coming weeks President Barack Obama, struggling with popularity ratings that show for the first time that more Americans disapprove of him as their president than approve, will make what may well prove to be the most critical decision of his presidency: he will name his candidate to succeed on the benches of the US Supreme Court the retiring John Paul Stevens, who celebrates his 90th birthday on 20 April. The choice is crucial for Obama, because the courtly Stevens - despite having been appointed by President Gerald Ford, a Republican, nearly 35 years ago - is now undisputed leader of the liberal rump on the nine-member Supreme Court, and therefore an essential ally for a Democratic president.
By present-day US standards, in fact, Stevens is downright left-wing. He became firmly opposed to the death penalty, pushed for the constitutional rights of prisoners in Guantanamo Bay, and was even a supporter of gay causes. He led the dissenters in the 5-4 vote that put George W Bush rather than Al Gore into the White House after the disputed 2000 presidential election. He wrote during those contentious days that although the true winner might never be established for certain, "the identity of the loser is perfectly clear. It is the Nation's confidence in the judge as an impartial guardian of the rule of law."
His will be quite an act to follow, therefore, when the Supreme Court reconvenes on 4 October after its summer break. But Obama is faced with a dilemma. Nominating Supreme Court judges, after all, is perhaps the single most important and long-lasting power a US president has. If Stevens's successor matches him for durability, he or she could well have a decisive say on major issues such as gun control, the death penalty, abortion, or gay marriage, until 2045 - by which time Obama himself will be a doubtless sprightly 84-year-old. Justice Stevens himself, in fact, wielded his sometimes considerable power during no fewer than seven presidencies.
The problem for Obama is that he cannot afford to risk a protracted battle with Republicans over a long, hot summer - knowing that, following the Democrats' loss of Senator Ted Kennedy's seat last February, the Republicans could even stage a filibuster in the Senate to thwart his choice. His selection will be calibrated in order to appeal to a wide range of demographics across the US political spectrum.
It was all so much more simple in 1975. Then President Ford could announce that Justice Stevens was "the finest legal mind I could find"; the Senate spent five minutes discussing his nomination, and Stevens duly breezed into the Supreme Court by a 98-0 vote.
But the days of such bipartisanship are long since over, and the country is politically more polarised than at any time since the civil war. President Obama has already appointed a team to scrutinise the political and judicial pasts of ten or so possible nominees to make sure they have no skeletons in their cupboards that Republicans or troublesome Democrats could exploit. I know one ideal candidate whom Obama also knows personally and would like to nominate, but when she was a law student she espoused some then-fashionable feminist and radical views in her writings. She has already been crossed off the list.
I mooted the possibility in these pages not long ago that Obama might nominate Hillary Clinton, but in the present climate nobody with a politically partisan past would stand a chance of ratification by the Senate. There are now only two women sitting on the Supreme Court benches, however. One of them, Justice Ruth Bader Ginsburg, a Bill Clinton nominee, is 77 and is suffering from pancreatic cancer. I would be very surprised indeed if Obama's final choice is not a woman.
The current front-runner is 49-year-old Elena Kagan, currently solicitor general - a proven Obama loyalist who has no paper trail of controversial writings and was once dean of Harvard Law School (which Obama also attended). Her relative youth is another plus. Next in the running is Diane Wood, 59, a federal judge in Chicago (in effect, Obama's home town) whose qualifications are equally strong - except that she is a staunch supporter of abortion rights. She, too, may prove too partisan.
My own hunch is that Obama's preference could well end up being 54-year-old Leah Ward Sears, a former chief justice of Georgia's Supreme Court. She is black and has impeccable credentials. She would contrast well with Sonia Sotomayor, the former federal court appeals judge of Puerto Rican descent whom Obama chose last year, but who has had a disappointingly lacklustre eight months on the benches so far.
The third alternative - gasp, gasp - is a man, Merrick B Garland (who incidentally was born in Chicago). A 57-year-old federal court judge in Washington, DC, he would perhaps command the most bipartisan support, but is unlikely to become the Stevens-type judicial activist that Obama would prefer.
The irony is that, whoever is chosen, the Supreme Court of the Obama era will end up being more right-wing than the current one - or even that of the best-forgotten days of George W Bush. Justice Stevens said that no Supreme Court judge should be afraid of "learning on the job", which, in his case, meant moving steadily to the left while America itself drifted steadily to the right. In 2010, no Obama nominee with a record of judicial decisions like that of Stevens could count on being confirmed by the Senate in these bitterly partisan days.
This, alas, is the reality of the new America. We'll miss you, judge.