One of the early tests of Barack Obama’s political skills came when he was a law student at Harvard University in the late 1980s and early 1990s.

In the midst of intense campus debates over faculty diversity and other divisive issues, Mr. Obama became the first black student to be elected president of the Harvard Law Review. At the law journal, he presided over difficult discussions among intellectuals with widely different views. Yet his professors say he was able to set an amicable tone and, at the same time, hold fast to his own beliefs.

In the fourth of our series of profiles of the leading candidates for president, we take a look at how Mr. Obama has won the favor of many in academe and the kind of “professorial president” he might make if he were elected.