S.R. Sidarth, a Democratic volunteer of Indian descent, was videotaping an Allen campaign event when the senator pointed to him and twice called him "Macaca." Macaca is a genus of monkeys that includes macaques, and is also considered a racial slur in some parts of the world.
"This fellow over here with the yellow shirt — Macaca or whatever his name is — he's with my opponent," Allen said.
He noted that his opponent, Democrat Jim Webb, was raising money in California, then told the crowd of about 100 supporters: "Let's give a welcome to Macaca here. Welcome to America and the real world of Virginia."
Sidarth, who was born just outside Washington in Fairfax County, Virgnia, said he felt Allen was singling him out by race.
Webb's campaign posted the video on YouTube, then alerted reporters. Within days of the Aug. 11 rally, it became a dominant political story and grist for late-night talk shows and Comedy Central's "The Daily Show With Jon Stewart."
Allen on Wednesday tracked down a phone number for Sidarth at the University of Virginia, where the 20-year-old had returned for his senior year, and apologized to him, said campaign manager Dick Wadhams.
"Senator Allen made a heartfelt apology," Wadhams said. "He told Sidarth he thought he would see him on the campaign trail, but Sidarth had headed back to U.Va., so we Googled his name, found his number and the senator called him this morning."
The Republican senator is seeking a second term while also exploring a potential 2008 presidential bid.
Wednesday night, Allen joined President Bush for a private fundraiser in the Virginia suburbs of Washington.
The damage will haunt Allen for a while, said Merle Black, a political scientist at Emory University in Atlanta and a specialist in presidential and congressional races.
"It just raises questions about his judgment and how sincere he is in how he deals with these kinds of issues," Black said.
Wadhams on Saturday had sent a memo to Republican leaders decrying a media "feeding frenzy" over the remark, saying it "did not warrant coverage in the first place," and accusing Democrats of trying to "play the race card."
Webb's campaign and the Democratic Senatorial Campaign Committee said that by dismissing the seriousness of the remarks, Allen's campaign was hardly remorseful.
The video will be hard for Allen to shake because it shows him pointing to Sidarth and singling him out for derision, and because he smiled as he needled Sidarth, seemingly enjoying the moment, Black said.
Republican strategists agreed it was damaging but said it need not doom Allen politically.
"Senator Allen needs to make it clear that he made a mistake, that this was obviously something he should not have done," said Mike Mahaffey, a former Iowa Republican Party chairman.
Iowa's nominating caucuses rely on one-to-one politics, giving Allen a chance to personally appeal to voters and convince them the incident was an aberration.
"If he can come across as sincere in that regard, it will not hamper him in Iowa," said Mahaffey, a GOP activist with a law practice in Montezuma, Iowa.
To remain a strong presidential contender, Allen needs to beat Webb convincingly, Black said.
"If it's close, that would be a sign of weakness," he said.