If John G. Roberts Jr. is confirmed as William H. Rehnquist's successor on the Supreme Court, the country will have not only a new chief justice but also a new political entity: the Roberts Court. We speak easily of the Rehnquist Court or the Warren Court, managing to identify those complex institutions with a single individual. But how does a chief justice put his stamp on the court?

At a political moment that is as polarized as any in recent memory, many Americans crave a court that, unlike the current White House and Congress, will follow a moderate path, and they are looking anxiously to Roberts's ideology for hints about the court's direction. A chief justice's judicial philosophy is important; but at the end of the day he has only one vote among nine. The most effective tools that a chief justice has at his disposal for shaping a court have less to do with his ideology than with his temperament, which shapes his personal skills as a cajoler, diplomat and unifier -- in other words, as a boss for an unusually independent group of prima donnas.

Throughout history, the chief justices who have been best able to preserve the court's reputation and legitimacy have been those with the most judicious dispositions. A chief justice's responsibilities are mostly procedural and organizational; it's his prerogative, when he is in the majority, to write the opinion for the court or to assign the opinion to a justice he believes will reflect his legal views, as part of his broader efforts to build consensus behind the scenes. John Marshall, who served from 1801 to 1835 and is widely considered the greatest chief justice in American history, was especially deft in exercising these powers. Marshall took office without judicial experience (in fact, 11 of the 16 chief justices have been appointed to the court without previously serving on it as associate justices), but like John Roberts, he had a reputation for an ability to argue both sides of an issue, for his bipartisan friendships and, above all, for a lack of pretense and a good nature. ("I love his laugh -- it is too hearty for an intriguer," wrote his friend and colleague Joseph Story.)

Marshall's skill in establishing convivial personal relations among his fellow justices helped him to cement the court's authority at a vulnerable moment in its early history. Recognizing the virtues of leading with a light touch, Marshall wore a simple black robe rather than the scarlet and ermine that were traditional at the time. And he insisted that his colleagues room together in the same boarding house, so that they could discuss cases over glasses of his excellent Madeira. As a result of his sensitivity to the views of his political antagonists (with the notable exception of Thomas Jefferson, whom he detested), Marshall was able to steer the court toward a middle ground and to speak for a unanimous court on the most divisive issues of his age.