For many of those students, the start of the academic year last week meant returning to a campus that spent much of the past year debating what they did and how the university responded. Harvard, which has never said how many students were required to withdraw, also declined to say how many had re-enrolled.

“It’s weird because I think everybody knows why I was gone, and it’s what they were talking about the whole time, but nobody says anything to my face,” one of the returning students said. Like other students in the group who granted interviews, he insisted on anonymity to prevent his name from being publicly tied to cheating.

Students who were punished accepted varying degrees of blame, ranging from one who said he warranted nothing more than a stern lecture, to another who said his suspension was fully deserved. All expressed concern about their transcripts bearing black marks that would be seen by graduate schools and prospective employers.

While many of the accused students hired lawyers, several of those lawyers said that as far as they knew, none had sued Harvard.

Introduction to Congress was taught by Matthew B. Platt, an assistant professor of government, along with 11 teaching fellows, graduate students who led discussion sessions. From previous years, it had a reputation for being easy, which Dr. Platt reinforced in early 2012, students said, by telling them that attendance was not essential and that he gave many A’s.

But the semester brought a sharp turnabout. Students reported that grading got tougher and exam questions became harder and more confusing; many of them speculated that Dr. Platt had been pressured by someone above him to change his ways. Dr. Platt has not spoken publicly about the matter, and he and the teaching fellows did not reply to interview requests. Government 1310 has not been offered since spring 2012.

Instructions on the take-home final allowed the use of books, notes and the Internet, but forbade discussing it with others. But in grading the exams, Dr. Platt found strong similarities among some of them, even verbatim repetition, down to the same typographical errors.