This preference for narrow, bipartisan rulings over broad ideologically polarized ones is at the heart of Roberts' vision for the court's role in American life. When he became chief justice, in 2006, he said in interviews that he would try to get his colleagues to avoid polarized 5-4 decisions by persuading them to care more about the court's institutional legitimacy than about their own ideological agendas. Since then, Roberts has had mixed success in achieving this goal, largely because Kennedy, the swing justice, prefers sweeping rulings to narrow, technical ones.
In the landmark health-care case last year, Roberts proved that he meant what he said. He joined the liberal justices in upholding President Obama's health-care mandate on technical grounds because he felt the court's bipartisan legitimacy required it. Last week, Roberts was even more successful as a bipartisan leader of the court.
Defying expectations, a nearly unanimous court avoided a broad ruling in refusing to strike down the University of Texas' affirmative-action program. Instead, the justices sent the case back to the lower courts. Roberts had similar success in the California marriage-equality case, where an unusual coalition of liberal justices joined his decision to dismiss the case for lack of standing. This had the effect of affirming a lower-court decision recognizing a right of marriage equality in California, but failed to set a broader national precedent.
By contrast, in cases where Kennedy cast the tie-breaking vote, the court spoke expansively rather than narrowly. The 5-4 Windsor decision striking down the federal government's denial of marriage benefits to gays and lesbians declared broadly that "the resulting injury and indignity is a deprivation of an essential part of the liberty" protected by the Constitution. Marriage-equality supporters will be able to invoke Kennedy's sweeping language to try to establish a national right to gay marriage in future cases.
And the 5-4 Shelby decision striking down the part of the Voting Rights Act that requires certain states but not others to get approval from the federal government before changing their voting procedures is similarly sweeping. Its dismantling of a core provision of the Voting Rights Act of 1965 shows a refusal to defer to elected officials on the question of who gets to decide the best way to avoid racial discrimination in voting: Congress or the courts?
The end-of-term decisions confirm that Roberts hasn't reinvented himself as a liberal minimalist after his vote in the Obamacare decision last year. It was Roberts himself who wrote the 5-4 decision striking down Section 4 of the Voting Rights Act. In other words, when Roberts is able to persuade liberal justices to join him in a narrow bipartisan ruling, he will do so, but when he can't get liberal votes, he is willing to join the polarizing 5-4 decisions along predictable ideological lines that he pledged to avoid.
But by and large, this term represents a triumph for Roberts' leadership. Defying expectations, he constructed bipartisan coalitions in several of the most polarizing cases of the year. And the court also issued unanimous rulings in other important cases - holding 9-0 that human genes can't be patented, for example.
Although the justices will return next year to a series of other controversial cases, including a new look at the future of affirmative action, one thing is now clear. At least some of the time, the Kennedy Court has become the Roberts Court.
Jeffrey Rosen is president and CEO of the National Constitution Center. E-mail him at firstname.lastname@example.org.
For more on this term's court cases, visit blog.constitutioncenter.org.