When long-serving Justice John Paul Stevens announced last week his intention to retire, Obama promised to "move quickly" to name a replacement.

Three names in the running with Sonia Sotomayor immediately surfaced: appeals judges Merrick Garland and Diane Wood and U.S. Solicitor General Elena Kagan. Activist groups allied with the Republicans indicating that they would put up a fight over Wood, largely because of her rulings on abortion, probably not object to Garland and hadn't made up their minds about Kagan, a former dean of Harvard Law, because she has never been a judge. Another name that has frequently come up this week is that of former Georgia Supreme Court Justice Leah Ward Sears, one of the most liberal jurists to ever sit on the state's highest court.

Both sides have laid down broad - and intentionally vague - criteria about what type of candidate they want the president to nominate. Senate Republicans have said they want a nominee who is in the "mainstream," who will interpret the law, not make it.

Obama said his nominee must have an independent mind, a record of integrity and a dedication to the rule of law. And, as he did with Sotomayor, the additional requirement of real-life experience on how the law affects ordinary Americans. Many suspect that's code for "I plan to pick someone who is willing to ignore the concept of 'impartial justice' from time to time in order to further a liberal social agenda.'"

To avoid a fight altogether, Obama faces a difficult and perhaps impossible political calibration - a justice liberal enough to satisfy Senate Democrats, but moderate enough not to unduly alarm Senate Republicans. Liberal Democrats, still smarting from what they felt were sellouts on health care reform, will agitate for one of their own, especially because Stevens is the most liberal justice on an increasingly conservative court.

The Senate Judiciary Committee that will hold the confirmation hearings is one of the most contentious and ideological in Congress, with some of the Senate's most liberal Democrats and conservative Republicans. The hearings can set off fireworks, but they're rarely informative because the dynamics require the nominee to be as noncommittal and unforthcoming as possible.

The committee is not a problem for the White House. Democrats have a 12-to-7 advantage. The full Senate could be if the Republicans, with 41 votes in hand, set out to filibuster the nomination. But over the weekend, Republicans were at pains to say that they would resort to the filibuster only in "extraordinary circumstances."

Only once has a Supreme Court nominee been filibustered, and that was 42 years ago. And, with the election coming up, it would open Republican lawmakers to charges of obstructionism. But considering the battering that Democrats gave judicial nominees by recent Republican presidents, that would certainly be a case of "turnabout is fair play."

The chances that Obama will nominate a conservative - or even a conservative-leaning jurist - to the court, are about the same as the chances of heavy snow during Marietta's upcoming July Fourth parade. But he would do himself - and the country - a favor by at least nominating a moderate to replace Justice Stevens.