Liberal stalwart John Paul Stevens is now officially retiring, and President Obama is preparing to nominate a successor to fill his seat on the Supreme Court. Naturally, D.C. is buzzing about who that will be. Equally weighty, though, is the question of whether Republicans will gird for battle and try to block Obama's pick in the Senate, now that they have enough votes to sustain a filibuster. (See more at The Week's Sunday Talk Show Briefing.) Here's a look at the emerging situation:

What is Obama looking for in a nominee?
Obama says he'll choose a jurist with "an independent mind, a record of excellence and integrity, a fierce dedication to the rule of law," and an understanding that "in a democracy, powerful interests must not be allowed to drown out the voices of ordinary citizens."

Who are the top candidates?
Pundits generally agree that the frontrunners include current Solicitor General Elena Kagan, and federal appellate court judges Merrick Garland and Diane Wood. On the other hand, notes Richard Adams in The Guardian, don't place too much store in predictions: "Few of those lists included Sotomayor's name last time around." (For just such a list, see The Week's run-down of the Top 5 frontrunners.)

Who would be easiest to get confirmed, and hardest?
Obama's safest bet for an easy confirmation seems to be Garland, 57. A former prosecutor, Garland sits on the Washington, D.C. circuit, and is said to be close to conservative Chief Justice John Roberts. Kagan, 49, would likely prompt a "fake fight" from Republicans, says Slate's Christopher Beam, but the Senate has already confirmed her once, to be solicitor general. If Obama wants a real fight, he'll pick Wood, 59, the most liberal of the three.

Why would Obama want to pick a fight?
With the wind at Obama's back from his big victory on health care reform, it could be a good time to push hard for a justice who "reflects his liberal ideals for the court," says Joan Biskupic in USA Today. Also, since Stevens is one of the "liberal seats" on the court, this is Obama's best shot to pick a potential leader for the court's liberal wing, says Seth Stern in Slate, since he'd face strong pressure to choose a moderate if one of the conservatives "unexpectedly retires."

What are the chances of a Republican filibuster?
"Tiny," according to Sen. Chuck Schumer (D-NY), though Republicans aren't taking the option off the table. And with key midterm elections coming up, it could even be in their best political interest to set up a big, base-riling showdown, says The Guardian's Adams. "Why hand the White House and the Democrats another victory before then?"

So why wouldn't the GOP filibuster?
The court's ideological makeup will still lean conservative, no matter who Obama picks. And "open warfare" by the Republicans could "simply further alienate the middle," says Jazz Shaw in Hot Air. The GOP can score political points without that risk, "simply by pointing out the record" of the inevitably liberal nominee during a drawn-out confirmation process.

Sources: USA Today, Slate (2), Hot Air, NY Times, Washington Post, The Guardian, White House