WASHINGTON – When Chief Justice John Roberts joined with the court’s liberal justices to uphold President Obama’s health care law, it was historic in more ways than one: It was only the second time in his seven years on the court that he provided the winning vote for the left to prevail over the conservative justices.

That statistic alone should be enough to cool hopeful chatter from some liberal political commentators that perhaps Roberts is showing signs of becoming the next David Souter. Souter, nominated to the court in 1990 by President George H.W. Bush, eventually became a fairly reliable liberal vote.

But it does point to another fact about the Supreme Court term that ended last week: In cases that divided the court into its usual ideological camps, liberals were in the majority as often as conservatives.

Justice Anthony Kennedy, who typically provides the decisive vote when liberals and conservatives disagree, sides about two-thirds of the time with conservatives. This term, according to statistics at SCOTUSblog, he split the difference evenly.

And on the two issues most likely to define the court’s term – health care and Arizona’s get-tough law on illegal immigration – liberal justices Ruth Bader Ginsburg, Stephen Breyer, Sonia Sotomayor and Elena Kagan were in the majority.

The limit of federal power was the overarching theme of the court’s deliberations this term, and it delivered a mixed verdict.

Kennedy and Roberts parted ways with conservatives Antonin Scalia, Clarence Thomas and Samuel Alito in the Arizona case. Kennedy’s majority opinion was a solid affirmation that the federal government must play the pre-eminent role in immigration policy and that states must be careful in trying to supplement it.

The health-care ruling, like the immigration decision, was an important political win for the Obama administration. But it came with new restrictions on federal authority. Roberts and Kennedy joined the other conservatives in saying the requirement that almost all Americans must buy health insurance was not constitutional under Congress’s authority to regulate interstate commerce.

“The Commerce Clause is not a general license to regulate an individual from cradle to grave,” Roberts wrote, although he found the individual mandate constitutional under Congress’s taxing authority.

Liberals were on the prevailing side in several key criminal justice cases.

The court extended its line of cases requiring courts to treat juvenile offenders different from adults by banning mandatory life sentences even if the conviction is for murder. By a separate 5-4 vote, it extended the right to effective counsel to plea offers, recognizing that few criminal cases go to trial.

And Kennedy joined the liberals to rule that Congress intended more lenient sentences it created for crack-cocaine offenders to apply even for some of those who committed their crimes before the law was signed.

Those victories hardly make a trend. According to the SCOTUSblog, Kennedy and Roberts were most likely to be in the majority, while Ginsburg and Breyer were the least likely.