Harvard students suspected in a major cheating scandal said on Friday that many of the accusations are based on innocent — or at least tolerated — collaboration among students, and with help from graduate-student teachers who sometimes gave them answers to test questions.

Students said they were tripped up by a course whose tests were confusing, whose grading was inconsistent, and for which the professor and teaching assistants gave contradictory signals about what was expected. They face the possibility of a one-year suspension from Harvard or revocation of their diplomas if they have already graduated, and some said that they will sue the university if any serious punishment is meted out.

In years past, the course, Introduction to Congress, had a reputation as one of the easiest at Harvard College. Some of the 279 students who took it in the spring semester said that the teacher, Matthew B. Platt, an assistant professor of government, told them at the outset that he gave high grades and that neither attending his lectures nor the discussion sessions with graduate teaching fellows was mandatory.

“He said, ‘I gave out 120 A’s last year, and I’ll give out 120 more,’ ” one accused student said.

But evaluations posted online by students after finals — before the cheating charges were made — in Harvard’s Q Guide were filled with seething assessments, and made clear that the class was no longer easy. Many students, who posted anonymously, described Dr. Platt as a great lecturer, but the guide included far more comments like “I felt that many of the exam questions were designed to trick you rather than test your understanding of the material,” “the exams are absolutely absurd and don’t match the material covered in the lecture at all,” “went from being easy last year to just being plain old confusing,” and “this was perhaps the worst class I have ever taken.”