The received wisdom at the end of the most recent Supreme Court term is that because of his swing vote, Justice Anthony Kennedy is more in control of the court than the new chief justice, John G. Roberts Jr.

It's a nominally plausible theory, given that Kennedy played a similar pivotal role in previous years with the now-retired Justice Sandra Day O'Connor. In those days, the two often found themselves disproportionately powerful as they staked out ground between the court's more ideological members.

But, it's a misleading picture of what's happening now — partly because Kennedy is often deliberately speculative and partly because Roberts has at least the nascent but constructive capacity to span partisan division.

Kennedy without O'Connor is like Rodgers without Hammerstein. Oscar Hammerstein wrote lyrics that made songs both memorable and understandable. O'Connor had a comparable gift for creative expression, even as originalists sometimes wondered if she was always reading from the founders' constitutional songbook.

For better or worse, it was O'Connor who had to be satisfied. It was her "reasonable objective observer" who would cast a suspicious eye at public religious displays. And it was her assessment — not Kennedy's — of the University of Michigan's practices that allowed racial diversity to be a factor in admissions.

Kennedy, like Richard Rodgers, would often join O'Connor with an accompanying melody. But the words that lower courts would remember were hers.

Kennedy and O'Connor both concluded, for example, that it was wrong for Texas to single out private, consensual homosexual sex acts for criminal punishment. But it was O'Connor's separate concurrence that made sense of the judgment — pointing out that it is inequitable for a state to punish unmarried intimacy between people of one sexual orientation but not the other. Despite the troubling lack of deference to state law, O'Connor's rationale was at least anchored in the equal-protection text of the Constitution, while Kennedy's hung somewhere in midair exploring what he called "spatial and transcendent" liberties.

O'Connor's rationale was sufficient to keep the petitioner, John Lawrence, and his partner out of a Texas jail; Kennedy's expansive musings to this day provoke further litigation to allow same-sex marriage.

Kennedy's theorizing reveals a mind of great intelligence but makes it more difficult to strike bargains with him. O'Connor knew what she wanted as a specific outcome, so the liberal and conservative coalitions could make reasonable bids for her affections.

Kennedy's ruminations produce cases that have outcomes but no settled rationale. Thus, the scope of the Clean Water Act remains a mystery, beyond Kennedy's requirement for some as-yet-undefined "significant nexus" to U.S. waters; the exclusionary rule does not apply in no-knock cases, but it should not be seen as "in doubt"; and Salim Ahmed Hamdan, the Guantanamo detainee, deserves a tribunal more jurisprudentially spiffy than the president's military commissions because of the influence of the Geneva Convention, but it is "not necessary to decide" how to apply the convention.

If Kennedy by manner and approach chooses to do-si-do rather than lead the judicial dance, who then emerges as the dominant influence on the court? By virtue of seniority (and sheer intellectual feistiness), Justice John Paul Stevens, 86, is the organizing voice of the four-vote liberal view. Justices Antonin Scalia and Clarence Thomas remain the rock-solid right. Neither is sufficient to decide.

That returns focus to the center seat. And, after a year, Roberts has had remarkable appeal in this position as the nonlegislating umpire he described during his confirmation.

Roberts has a conservative mind but a diplomat's nature. His abiding concern is to keep the court within bounds on legal, rather than ideological, grounds. Because that is so, he has the capacity to draw votes from both sides on controversial and pedestrian cases alike.

Consider two examples: his unanimous opinion rejecting free speech and association claims against Congress' Solomon Amendment mandating equal campus access for military recruiters; and his opinion rejecting, on procedural grounds, a challenge to tax credits favoring in-state investment.

Roberts' collegial consensus-building here and elsewhere overwhelms Kennedy's ability to deploy his swing vote. The impact of the new chief justice was especially influential because he and Justice Samuel A. Alito Jr., the newest addition to the bench, share the founding vision of a more limited role for the court and have great affinity for each other (close to 90 percent agreement this term).

The fractious finale of Hamdan v. Rumsfeld, invalidating the president's military commissions, obscures more than it reveals because there Roberts was sidelined by recusal and unable to urge his colleagues toward consensus — or at least a more carefully tailored and clearly stated, not to mention succinct, opinion.

Roberts' ability to influence justices across the spectrum of ideas suggests that the most apt modifier for the court is neither "Kennedy" nor "Roberts" but "open-minded." The strengthening of this quality for the nation's highest tribunal ought not to be missed by outworn efforts that either pigeonhole the court by partisan label or make it a cult of personality.

Douglas W. Kmiec is a constitutional-law professor at Pepperdine University. He wrote this commentary for the Los Angeles Times.