Knit cap pulled down over his ears, shoulders hunched against the biting wind, Paul Nungesser was almost indistinguishable from the dozen or so other students traversing the steps of Columbia University’s Low Memorial Library one menacing December day. But a few of those students recognized him anyway, flicking their eyes up for a discreet peek before hurrying on to the last classes of the semester.

He has gotten used to former friends crossing the street to avoid him. He has even gotten used to being denounced as a rapist on fliers and in a rally in the university’s quadrangle. Though his name is not widely known beyond the Morningside Heights campus, Mr. Nungesser is one of America’s most notorious college students. His reputation precedes him.

His notoriety is the result of a campaign by Emma Sulkowicz, a fellow student who says Mr. Nungesser raped her in her dorm room two years ago. Columbia cleared him of responsibility in that case, as well as in two others that students brought against him. Outraged, Ms. Sulkowicz began carrying a 50-pound mattress wherever she went on campus, to suggest the painful burden she continues to bear. She has vowed to keep at it until he leaves the school.

Her story has been so compelling — and “Mattress Performance (Carry That Weight),” which doubles as her senior thesis for the visual arts department, so affecting — that large numbers of Columbia students have rallied around her. She has been honored with national awards. In October, students at more than 100 colleges carried their own mattresses (or pillows) to call attention to the problem of campus sexual assault.