Larry J. Sabato, one of Virginia's most-quoted political science professors and a classmate of Allen's in the early 1970s, said in a televised interview Monday that Allen used the epithet.
Sabato's assertion came on the heels of accusations by Dr. Ken Shelton, a radiologist who was a tight end and wide receiver for the University of Virginia in the early 1970s when Allen was quarterback. He said Allen not only used the n-word frequently but also once stuffed a severed deer head into a black family's mailbox.
Separately, the Washington Post reported that Christopher Taylor, 59, an anthropologist at the University of Alabama, said that during a visit to Allen's Virginia home in 1982, Allen referred to turtles in a pond on his property and said that only "the [racial slur] eat them."
The newspaper quoted Allen adviser Chris LaCivita as saying Taylor was lying. LaCivita described Taylor as a liberal activist.
The Post also interviewed two former Virginia athletes who asserted Allen frequently used racial slurs during his college years. The athletes were not identified.
Allen's campaign released statements from four other ex-teammates defending the senator and rejecting Shelton's claims.
LaCivita said Allen and Sabato were not friends nor did they associate with each other in college.
"Larry is obviously relying on words he heard from someone else," he said. "We believe it's completely inaccurate."
Sabato, director of the University of Virginia Center for Politics, would not tell the Associated Press how he knew Allen used the n-word. He told Chris Matthews on MSNBC that he did not know whether it was true that Allen used the word frequently while in college.
"I'm simply going to stay with what I know is the case and the fact is he did use the n-word, whether he's denying it or not," Sabato said.
Allen, a Republican, has been mentioned as a possible presidential candidate in 2008. Questions about racial insensitivity have dogged him during his re-election bid against Democrat Jim Webb.
Allen's use of the word "macaca" in referring to a Webb campaign volunteer of Indian descent in August prompted an outcry. The word denotes a genus of monkeys and, in some cultures, is considered an ethnic slur. But the senator insisted he did not know that and had simply made up the word.
Allen vehemently denied that he used the n-word.
"The story and his comments and assertions in there are completely false," Allen said during an interview with AP reporters and editors. "I don't remember ever using that word and it is absolutely false that that was ever part of my vocabulary."
Shelton said Allen used the n-word only around white teammates.
Shelton said the incident with the deer head occurred during their college days when he, Allen and another teammate who has since died were hunting on a farm the third man's family owned near Bumpass, Va., 40 miles east of the university.
Shelton said Allen asked the other teammate where black families lived in the area, then stuffed a deer's head into the mailbox of one of the homes.
"George insisted on taking the severed head, and I was a little shocked by that," he told the AP. "This was just after the movie `The Godfather' came out with the severed horse's head in the bed."
Shelton said he came forward because of Allen's presidential prospects and the "macaca" incident.
"When I saw the look in his eye in that camera and using the word `macaca,' it just brought back the bullying way I knew from George back then," he said.
Shelton described himself as an independent who has supported Democratic and Republican candidates. He said he regretted that he had not spoken against Allen in the early 1980s, when he first entered politics. Shelton said he began writing down his recollections as Allen's career "ascended to heights I never could have imagined."
Other former teammates rushed to the senator's defense.
Charlie Hale, a college roommate of Shelton's and an Allen campaign volunteer, said that he had hunted often with Allen, and "there was not even a rumor on the team" about the alleged deer incident.
Doug Jones, another Allen campaign volunteer who said he had roomed with Shelton, also dismissed the allegations. "I never heard George Allen use any racially disparaging word, nor did I ever witness or hear about him acting in a racially insensitive manner," he said.
Another former teammate, Gerard R. Mullins, said he recalled nothing racist about Allen.
"George had a strong personality, and I guess that's why he was a quarterback," Mullins, who is not close to Allen, said in a telephone interview.
Allen was sometimes confrontational with teammates, he said.
"He would kind of pick on everyone a little just to get a reaction," said Mullins. "From a football standpoint, if you were black or white it didn't matter. If you dropped a pass, he'd have something to say to you."
Shelton's claims came a week after a debate in which Allen bristled at questions about his Jewish ancestry. Allen later acknowledged publicly for the first time that his grandfather, a prisoner in a Nazi concentration camp, was Jewish, and on Monday he said both his maternal grandparents were Jews.
Explaining his initial reaction, Allen has said his mother swore him to secrecy when she told him about his ancestry last month.
Allen's father, the late George H. Allen, was a legendary football coach with the Los Angeles Rams and the Washington Redskins. Allen transferred from the University of California, Los Angeles, to Virginia when his father took the Redskins job.