I recently asserted that any of the four people on the list initially leaked by the White House would be an excellent nominee to succeed retiring Justice John Paul Stevens. (See "An Excellent Supreme Court Shortlist," 4/10/10, p. 15.) Now I’d like to argue that the wisest choice would be Judge Merrick Garland of the U.S. Court of Appeals for the District of Columbia Circuit.

I hasten to add that the consensus that Garland would be the least controversial, most easily confirmed nominee is the least of my reasons for praising him.

Nor is my personal relationship with Garland a substantial factor, although full disclosure is in order: We became friendly in law school, working together on the law review in the mid-1970s. We had dinner at each other’s homes years ago and, more recently, have met for lunch once or twice a year. He invited my wife and me, among many others, to his chambers to watch President Obama’s inauguration. Garland has been guarded about his views, and I know nothing about them beyond the public record. But I can testify — as can many others — that he is about as fair-minded, judicious, and straight as a straight-arrow can be.

To be sure, ranking Garland and the three other shortlisters — all people of outstanding integrity and intellect — is a close call.

Solicitor General Elena Kagan, the early betting favorite, would bring youth (she is 49; Garland is 57), charm, and substantial conservative as well as liberal support. The former Harvard Law School dean is unencumbered by much of a paper trail — her views on almost all of the big issues are unknown — or by as much real-world experience as the others.

With the long-expected announcement by Justice John Paul Stevens that he will retire by July, the coming summer could be dominated by a big confirmation battle — or perhaps just enlivened by a little skirmish, if President Obama picks a relatively uncontroversial nominee.

Many Republicans are spoiling for a fight to rev up their base for the coming elections. Some would depict any Obama nominee as an ultra-liberal eager to push the Court to the left, legislate from the bench, impose gay marriage by judicial decree, strip "under God" from the Pledge of Allegiance, invent welfare rights, require government-funded abortions, and free terrorists.

But, in fact, none — or at most one — of the four brainy and well-qualified public servants at the top of the shortlists that have made their way into the media from inside sources seems likely to move the Court left.

None of the four is clearly more liberal than Stevens, who is in turn a lot less liberal than, say, the late Justices William Brennan or Thurgood Marshall.

Stevens, who will still have one of the best minds on the Court when he turns 90 on April 20, has long insisted that he remains the old-fashioned judicial conservative and moderate Republican he was when President Ford appointed him in 1975. But the leftward drift of his opinions over the years has made him the senior member of the four-justice liberal bloc.

The four shortlisters are Solicitor General Elena Kagan; federal Appeals Court Judges Diane Wood of Chicago and Merrick Garland of the District of Columbia; and (though some count her out) Homeland Security Secretary Janet Napolitano. President Obama interviewed Kagan, Wood, and Napolitano last spring before choosing Sonia Sotomayor, an Appeals Court judge, to succeed Justice David Souter.

President Obama will not begin interviewing possible Supreme Court nominees until next week at the earliest, according to the White House. So what’s going on behind the scenes?

I don’t know for sure, but I can guess: Apart from vetting the leading prospects to flush out any character flaws, ethical issues or tax problems of the kind that have plagued some Obama nominees, the White House is probably devoting lots of attention to ideological vetting.

The goal of this process, which reportedly started long before it was clear that there would be a Supreme Court vacancy to fill, is to forecast insofar as possible how each prospect might rule on the biggest issues likely to come before the court in the next few years.

Like any president, Obama would prefer a nominee likely to uphold his own personal convictions on such issues as presidential war powers, abortion, racial affirmative action, voting rights, gay rights, religion in public life, assisted suicide, campaign finance reform and use of a litigation as a tool of social reform. Indeed, as someone who taught constitutional law, Obama may care more than most presidents about how his nominee will handle the big issues.

Ideological vetting of judicial nominees is a tricky business. A quotation often ascribed to President Lincoln helps explain why. Lincoln wanted to appoint a chief justice who would uphold the Union’s legal tender law, which required people to accept paper money as payment for private debts. "We cannot ask a man what he will do," Lincoln supposedly said, "and, if we should, and he should answer us, we should despise him for it. Therefore we must take a man whose opinions are known."

The federal judiciary will become markedly more conservative if McCain wins and markedly more liberal if Obama does. This shift will affect the outcomes of cases involving a host of ideologically charged issues, including abortion; gay rights; affirmative action; the death penalty; the rights of suspected terrorists; gun control; property rights; the environment; regulation; and big-dollar lawsuits against business.

To woo conservatives who have long mistrusted him, McCain has bashed "activist judges" who "legislate from the bench." He has cited Bush-appointed Chief Justice John Roberts and Justice Samuel Alito as his models of restraint.

Obama, who taught constitutional law at the University of Chicago, voted against the confirmations of Roberts and Alito, saying that they too often side with "the powerful against the powerless" and lack "empathy" for ordinary people.

The replacement of a retiring liberal justice by a conservative McCain appointee, or of a conservative by a liberal Obama appointee, could give the Supreme Court an ideologically solid majority for the first time in decades and gradually make a dramatic impact on the course of the law. That’s because the current Court is so closely — and deeply — divided. It has four liberals, four conservatives, and one justice (Anthony Kennedy) who swings depending on the issue.