Mr. Obama believes the court must never get too far ahead of or behind public sentiment, they say. He may have a mandate for change, and Senate confirmation odds in his favor. But he has almost always disappointed those who expected someone in his position — he was Harvard’s first black law review president and one of the few minority members of the University of Chicago’s law faculty — to side consistently with liberals.

Former students and colleagues describe Mr. Obama as a minimalist (skeptical of court-led efforts at social change) and a structuralist (interested in how the law metes out power in society). And more than anything else, he is a pragmatist who urged those around him to be more keenly attuned to the real-life impact of decisions. This may be his distinguishing quality as a legal thinker: an unwillingness to deal in abstraction, a constant desire to know how court decisions affect people’s lives.