The imminent retirement of Chief Justice William Rehnquist provides an opportunity to consider the role the Supreme Court has played in the U.S. political system. Putting it in the broadest possible terms: For most of its history, the Supreme Court has collaborated with the political coalition controlling the other branches of the national government, but occasionally the Court has placed itself in opposition to that coalition.

Take the Warren Court as an example. Frequently described as taking a leading role in advancing modern liberalism, the Warren Court is better understood as collaborating with the main lines of political development during the New Frontier and Great Society eras. As Lucas S. Powe has demonstrated, most of the Warren Court’s work brought into line “outlier” jurisdictions that had not yet brought their policies into conformity with a nationally predominant liberalism, and much of the remainder of the Court’s work eliminated hold-overs from an earlier time that lacked contemporary political support but that could not be taken off the statute books because of the force of political inertia. The Warren Court’s reapportionment decisions, for example, were enormously popular with residents in the growing suburbs even as they annoyed the politicians in place who understood that the decisions placed them in political peril. Even the desegregation decisions, which did overturn practices deeply embedded in the South, could be seen as enforcing a national view of proper race relations against a deviant region.

The alternative to the collaborative Court is the oppositional one, illustrated most notably in the Court’s history by the Supreme Court during the early New Deal. Yet, the history of that period, and particularly the Court-packing crisis of 1937 and its aftermath in the creation of the Roosevelt Court by means of judicial appointments, shows that the national political system is structured so as to make the oppositional Court an unstable or transitional institution. As Robert Dahl argued in 1957, the Supreme Court rarely sets itself in sustained opposition to a cohesive national political coalition.

Dahl’s analysis, and the idea of a collaborative Court, depends on there actually being a national political coalition. Yet, from the 1980s through the 2004 election we had divided government, with the presidency and Congress controlled by different parties (or, at least, with Congress functionally controlled by a party other than the president’s because of the ability even of minorities in the Senate to obstruct policy initiatives). The policy outputs of divided government were, in general, small initiatives punctuated with large tax cuts pushed through Congress under circumstances particularly favorable to such cuts. What was the Supreme Court’s role in the era of divided government?

Political scientists would say that divided government gave the Court essentially complete freedom to pursue whatever agenda its majority had. That’s because even if it offended one party with its rulings, that party couldn’t do anything about it: If the Court offended a Democratic Congress, a Republican president would veto any efforts to retaliate. But, notably, the Rehnquist Court took no large steps to revise constitutional law – despite occasional claims that the Court transformed the constitutional law of federalism. In some ways we can describe the Rehnquist Court as collaborating with a divided government – taking small steps equivalent to the small steps the political branches were taking.

The reason that the Rehnquist Court was a collaborative Court was that the Court was divided. There was, of course, a division between the Court’s “conservatives” and its “liberals,” but the more important division was within the camp of justices appointed by Republican presidents. Again, painting with a broad brush, I distinguish between traditional Republicans, the remaining heirs of the Nelson Rockefeller wing of the Republican Party, and modern Republicans, drawn from the Republican Party transformed by Barry Goldwater and Ronald Reagan.

Traditional Republicans have been internationalist in foreign affairs, opposed to the broadest versions of post-New Deal government regulation of business, and liberal-to-libertarian on modern social issues. Modern Republicans agree with traditional ones on the regulatory issues but disagree vehemently on the social issues.

John Paul Stevens and David Souter are the obvious exemplars of the traditional Republicans, Chief Justice Rehnquist, Antonin Scalia, and Clarence Thomas the modern Republicans. Most important, Justices Sandra Day O’Connor and Anthony Kennedy have pretty much acted as traditional Republicans.

Why they did so remains something of a puzzle. For Justice O’Connor, the reason may lie in her biography. She was a professional woman in suburban Arizona who became active in Barry Goldwater’s Republican Party in the 1950s. But, her location in Arizona aside, one would expect a person with those characteristics to have become a traditional Republican. Her experience in leading a closely divided state legislature may have pushed her in that direction as well. And, personal relations on the Supreme Court – and especially her reaction to what she regarded as Justice Scalia’s lack of politeness – may have pushed her away from the Court’s modern Republicans.

Justice Kennedy’s libertarian streak unifies his positions on the regulatory and the social issues. And, although the effects can easily be overstated, the pleasure he took in becoming an important figure in Washington’s social circles, circles where traditional Republicans (and Democrats) held sway, probably made it easier for him to be more traditional than modern in his Republicanism.

The division within the Court’s Republicans explains a great deal about the Rehnquist Court’s course. The agreement among all Republicans on questions of regulation meant that the Court would treat some degree of deregulation as required by the Constitution, but the traditional Republicans’ general acceptance of the post-New Deal regulatory state limited how far the deregulatory thrust could go. The disagreement among the Republican appointees on social issues meant that the liberals would prevail in cases involving those issues, not because the Court was dominated by the liberals but because the traditional Republicans joined the liberals.

What of the future? Here I return to the desegregation decisions. They show that even a Court that is generally collaborative can occasionally become a leader, not a follower, in the elaboration and enforcement of the national political coalition’s program. As Alexander Bickel suggested, sometimes the Court anticipates the future. Today we have a unified government, and some of the Rehnquist Court’s decisions, limited in scope though they were, can be seen as laying the groundwork for more dramatic moves that would be consistent with the goals of a unified conservative government. Once again, we might see the Supreme Court disciplining “outliers” who reject conservative positions on government regulation of business and on some of the social issues. An example of the latter might be a decision requiring that states include religiously affiliated schools in whatever school voucher programs they create.

Everyone expects that President Bush will have the opportunity to make several appointments to the Supreme Court. We can be reasonably sure that his nominees will be reliable modern Republicans. Then we would have truly unified government, with an unproblematically collaborative Court.

At least for a while. One can wonder, though, what would happen were a Democrat to regain the presidency while Congress and the Supreme Court remained in the hands of modern Republicans. (One would reasonably anticipate another impeachment proceeding, but that’s another matter.) The return of divided government with an undivided Supreme Court would probably lead the Court routinely to take positions that the Democratic president would regard as siding with Congress. Depending on the president’s political strength and ability, the president might treat this as a new constitutional crisis and go to the people on the question of transforming the Supreme Court. Whether such an appeal would be made, and whether it would succeed, of course cannot be known. But, I suspect, the experience would be more interesting than watching a modern Republican Court smoothly collaborating with modern Republicans in Congress and the presidency.