Now, Allen is running for office again. In 2012, he's a favorite to win the GOP nomination for the seat he used to hold. Webb recently announced that he wouldn't seek another term.
So how badly will this epic campaign blunder come back to haunt him in 2012?
It's important to remember that the "macaca" incident didn't completely sour Virginia voters on Allen last time around. Despite Allen's disastrous campaign, the 2006 race was a close one. Allen still led by single digits for much of it. Webb won by just over 7,000 votes, 50 percent to 49 -- this despite a strong wind for Democrats nationwide, and despite Webb's heavy campaigning against President Bush's handling of the wars in Iraq and Afghanistan.
This time around, things are looking pretty good for Allen. He could have to go up against a big-name Democrat if former governor Tim Kaine leaves the helm of the Democratic National Committee to run for the Senate. But the national momentum is much better for Republicans right now than it was in August 2006.
The "macaca" episode might not even come up too often -- particularly if President Obama's reelection campaign sets the tone in 2012.
"You've got a campaign for president, which is gonna be predominately focused on issues, and so people are going to be battling out over issues, and then all of a sudden an ad comes up attacking George Allen personally for something he said six years ago," and that won't seem to fit with the tone set by Obama's campaign, said a Virginia Republican strategist.
"Allen has to keep the campaign about issues, because if he keeps the campaign about issues, then from a tactical standpoint he's got the upper hand," said the strategist, who added that Democrats would lose the moral high-ground by bringing up Allen's awful 2006 blunder, if Allen and Republicans refrained from personal attacks themselves.
The Virginia Democratic Party says it's not certain it will make much of the "macaca" incident this time around, though such decisions will largely be up to the Democratic candidate and his or her campaign.
"I think Virginia, like America, is a very forgiving place, in that people will give you a chance to explain and move on from kind of one-off incidents that you wish you would have done better," said state party spokesman Brian Coy. "The thing that's tougher to forgive is six years of being mediocre at best as a U.S. senator."
If there are to be TV ads replaying the "macaca" incident in an attempt to damage Allen, it appears they'll most likely come from independent groups unaffiliated with either the sate party or the Democratic challenger's campaign -- a dynamic that emerges every campaign cycle in multiple states across the country. But the Republican strategist I spoke to makes a valid point: In 2008, President Obama sent a clear message that he did not want independent, soft-money groups airing below-the-belt ads about John McCain, and Obama '08 carefully controlled its message across the country.