WASHINGTON — The last week of the Supreme Court’s term told one kind of story, of a deeply divided court delivering historic victories to the Obama administration in immigration and health care cases. Those decisions, however, obscured a different story about the work of the court, one that unfolded over the last nine months.

A look back at the term just concluded reveals that the court, which has had a reputation for predictable ideological splits, has entered a new phase. This term, it sometimes worked with striking unanimity and assertiveness to review the actions of the other branches of government. Partly for this reason, its relationship to the Obama administration has often been a distinctly adversarial one.

When the court was divided, as it was in the immigration and health care cases, its voting often did not track the usual patterns. There is good evidence that Chief Justice John G. Roberts Jr. has worked hard to insulate his institution from the charge that it has political motivations, an accusation that it is especially vulnerable to because the court’s five more conservative members were appointed by Republican presidents and its four more liberal ones by Democrats.

It was not until Justice Elena Kagan joined the court in 2010 that the justices’ ideological positions largely tracked those of the presidents who appointed them. Under Chief Justice Roberts, the court has had substantial turnover. In the earlier versions of the Roberts court, Justices David H. Souter and John Paul Stevens, both appointed by Republican presidents, generally voted with the court’s liberal wing.