Chief Justice William H. Rehnquist has been absent from oral argument and court conferences for almost a month now, and speculation over who might replace him as chief has now lurched into high gear. While virtually everything we know about the severity of his thyroid cancer, his treatment, and prognosis remains purely speculative—and while he continues to work from home and plan for the court's annual Christmas party—the fact remains that if he's unable to join his colleagues on the bench in the coming weeks, he will likely have to step down. Last week the headlines screamed that Clarence Thomas was next in line for his job, although Antonin Scalia and Sandra Day O'Connor are also good possibilities—should President Bush wish to elevate a sitting justice. There is also great excitement over a pair of 4^th Circuit judges, Harvie Wilkinson III and J. Michael Luttig, as candidates for next chief. Emilio Garza, from the 5^th U.S. Circuit Court of Appeals, former Solicitor General Ted Olson, and Miguel Estrada figure high on that list, and over at SCOTUSblog, Tom Goldstein has filed a series of amicus briefs supporting the nomination of John Roberts, of the D.C. Circuit, as next chief.

The burning question underlying all this handicapping and odds-laying is still this: Does it matter who is tapped to be chief justice? Is there really a difference between, say, elevating an O'Connor to fill a potential Rehnquist seat and putting an Edith Jones—currently serving on the 5^th Circuit—directly into that spot? Rehnquist is fond of saying that the chief only has one vote and no one listens to him anyhow. So how much does it really matter who ultimately gets to be chief and who is merely an associate?

The answer is—as all great legal answers must invariably be—"It depends." Of the 16 chief justices, some have made an enormous impact and some have been both forgettable and forgotten. The formal powers of the chief justice don't sound all that enticing: He or she is essentially like a glorified Alice on the Brady Bunch—getting to do all the administrative grunt work with which no one else would possibly want to be bothered. He's the administrator of the court and manager of the court building. He serves on tedious collectives such as the Judicial Conference—an entity described as the "board of directors" for the federal judiciary. On top of all that, he has to act as harried class secretary—recording all the goings-on at case conferences, tracking who voted for what, and how dozens of opinions will be disposed.

Yawn.

The trick to understanding the chief justice's real role in shaping a court has to do with the myriad subtle ways in which any savvy administrator can effect vast policy changes. Having the authority to send around initial cases for discussion gives the chief justice tremendous power to shape the court's agenda, for instance, as does his power to introduce and offer the first vote at case conferences. Historically, some of the most powerful chief justices have exercised their influence by stifling dissent. In his first four years as chief justice, John Marshall (chief from 1801-1835) was so insistent that all opinions be unanimous that he simply authored all of them—save for those published per curiam (or unsigned)—himself. In those four years there was only one published dissent. As chief justice, William Howard Taft (1921-1930) espoused the same philosophy: Dissents fostered an appearance of uncertainty and were only a form of egotism anyhow, in his view. So over Taft's tenure, the high court issued unanimous opinions 84 percent of the time.

The big stealth power for any chief justice lies in his ability to assign written opinions whenever he votes with the majority in a case. If he votes with the minority, the most senior judge in the majority does the assigning. Chief Justice Charles Evans Hughes (chief from 1930-1941) regarded his opinion-assignment power as "a special opportunity for leadership" and, as a consequence, his "most delicate task." It doesn't sound like a big deal, but consider Warren Burger, chief justice from 1969 to 1986. In The Brethren, Bob Woodward describes Burger's assignment strategy as having two components: shifting his vote after conference so as to retain the assignment power (even if it meant voting against his originally stated views) and then assigning only lame opinions to his enemies.

According to Woodward, Burger's strategy was to keep all the big criminal law, racial discrimination, and free-speech cases away from his ideological "enemies," as he called William Brennan, Thurgood Marshall, and William O. Douglas—as well as to author all the unanimous opinions himself. That way it looked as if his wisdom was indisputable and his leadership unparalleled. Burger also did a tremendous amount of politicking as chief—giving policy speeches and attending conferences, as well as shamelessly pressuring the other justices to vote with him for blatantly political reasons.

Rehnquist is not at all creepily Machiavellian, like Burger. In fact, while he's known for making the case conferences extremely brief and businesslike, he's also acknowledged as more than evenhanded when it comes to handing out opinions—occasionally even assigning himself a crappy one, just to be fair. Still, there is little doubt that Rehnquist will go down in the books as an extremely influential chief justice, regardless of the fact that O'Connor and Anthony Kennedy will ultimately have had far more influence over the case law emerging from the Rehnquist Court than he did.

As an amateur historian, Rehnquist knows this well. In his 2001 book, The Supreme Court, he attempts to explain why John Marshall left such a massive footprint on the political landscape by reminding readers that Marshall was not the first chief justice, merely the first chief justice anyone remembers. "Marshall's predecessors were probably both better-known men in the young republic at the time of their respective appointments than Marshall was in 1801, but neither appeared to see any opportunity in the post in which they served." [Italics mine.] Marshall was acutely aware of the political potential for himself and the Supreme Court, and he seized it, nabbing all of constitutional history right along with it. As Rehnquist notes in his book, many of the most famous chief justices were not the most brilliant jurists. They were big-picture operators—with one eye on the law and the other on the Washington political scene. This is how Rehnquist has made such a significant impression on the court: not with eloquent opinions (his opinions tend to be short and workmanlike) or obsessive professorial absorption in the nuance of the law. He will be remembered instead as a great administrator, the head of an exceptionally collegial court, a savvy observer of history and government, and a man who saw many of his political views morph from the extreme minority to the law of the land.

Does it really matter who steps into the chief justice's striped robe? It might. A canny politician or rabid ideologue can use all these seemingly trivial powers to wrench the court onto a vastly different trajectory, whereas a bookish or naive successor could just fade back into the red velvet curtain. Layer this uncertainty over all the other uncertainties surrounding the court's future, and it's just one more question mark, as the great confirmation wars begin.

Dahlia Lithwick is a Slate senior editor.