Many American presidents have been lawyers, but almost none have come to office with Barack Obama’s knowledge of the Supreme Court. Before he was 30, he was editing articles by eminent legal scholars on the court’s decisions. Later, as a law professor, he led students through landmark cases from Plessy v. Ferguson to Bush v. Gore. (He sometimes shared his own copies, marked with emphatic underlines and notes in bold, all-caps script.)

Now Mr. Obama is preparing to select his first Supreme Court nominee to replace retiring Justice David H. Souter. In interviews, former colleagues and students say they have a fairly strong sense of the kind of justice he will favor: not a larger-than-life liberal to counter the conservative pyrotechnics of Justice Antonin Scalia, but a careful pragmatist with a limited view of the role of courts.

“His nominee will not create the proverbial shock and awe,” said Charles J. Ogletree, a Harvard professor who has known the president since his days as a student.