What does the video show? Not much. Indeed, new interviews show that a much-viewed YouTube recording cited as evidence by conservatives was actually shot well after the time in question.
It was March 20, near the end of the bitter health care debate, when Reps. John Lewis, Andre Carson and Emanuel Cleaver say that some demonstrators, many of them tea party activists, yelled the "N-word" as the congressmen walked from House office buildings to the Capitol.
Stung by the charges of racism, conservatives and tea party activists insist it never happened. And one of them is offering big money if anyone can prove it did.
With so many media and citizen cameras at the demonstration, any epithets would have been caught on tape, says Andrew Breitbart. He's the web entrepreneur who released the video of ACORN workers counseling actors posing as a pimp and prostitute, and has pledged $100,000 to the United Negro College Fund if anyone provides proof of the epithets.
"It didn't happen," said Breitbart, who wasn't there. "This is 2010. Even a racist is media-savvy enough not to yell the N-word."
The dispute pits the lawmakers - one of them, Lewis, is a leader and survivor of 1960s civil rights battles - against conservatives determined to counter claims of racism within the predominantly white and middle-aged tea party movement. The criticism has proven a distraction to a nascent movement pushing a unified message of fiscal conservatism and limited government.
The issue still echoes in the media and blogosphere.
"Listen, I was there," Carson, D-Ind., said in an interview. "In many regards I think (the challenges are) a veiled attempt to justify actions that are simply unjustifiable. I think we need to move toward a dialogue that explores why this kind of divisive and reprehensible language is still making it into our political debate."
A fourth Democrat, Rep. Heath Shuler of North Carolina, who is white, backed up his colleagues, telling the Henderson (N.C.) Times-News that he heard the slurs.
A reconstruction of the events shows that the conservative challenges largely sprang from a mislabeled video that was shot later in the day.
Breitbart posted two columns on his Web site saying the claims were fabricated. Both led with a 48-second YouTube video showing Lewis, Carson, other Congressional Black Caucus members and staffers leaving the Capitol. Some of the group were videotaping the booing crowd.
Breitbart asked why the epithet was not captured by the black lawmakers' cameras, and why nobody reacted as if they had heard the slur. He also questioned whether the epithets could have been shouted by liberals planted in the crowd.
But the 48-second video was shot as the group was leaving the Capitol - at least one hour after Lewis, D-Ga., and Carson walked to the Capitol, which is when they said the slurs were used.
Questioned about using a video on his Web site from the wrong moment, Breitbart stood by his claim that the lawmakers were lying.
"I'm not saying the video was conclusive proof," he said.
Lewis declined to discuss the issue with The Associated Press. Asked whether the epithet was used, his spokeswoman said: "Yes. Congressman Lewis did hear the N-word yelled from the crowd."
Carson described leaving the Cannon House Office Building for votes and bumping into Lewis in the elevator. They chose to walk outside to the Capitol, rather than through the underground tunnels.
Conservatives say Democrats staged a march through a hostile crowd to instigate a reaction. Carson said there was no such plan: It was just the first day of spring.
Soon after leaving Cannon, "I hear someone say it," said Carson, a former police officer. "You see one or two tea party people kind of look at him, and then you hear it again as we're walking. Then we walk across (Independence Avenue), and that's when it starts getting deeper."
Carson said he heard it coming from different places in the crowd. "You heard it in spurts, in the midst of 'Kill the bill. Kill the bill."'
"One guy, I remember he just rattled it off several times. Then John looks at me and says, 'You know, this reminds me of a different time."'
Cleaver, D-Mo., was walking a distance behind Carson and Lewis. He says he heard the epithet and was spit on. Capitol police handcuffed a man after Cleaver said he was spit on, but Cleaver told reporters that he did not want to press charges. No arrests were made. The moment was captured on video; debate continues over whether it shows any spitting.
In a separate case, Rep. Barney Frank, D-Mass., who is gay, said he was called "faggot."
On Fox News, Bill O'Reilly discussed the issue on four of his shows, beginning March 22. The first segment led with clips from the 48-second video and featured Dana Loesch, a radio talk-show host who accused the congressmen of fabricating their claims.
O'Reilly said, "Just because it's not on tape doesn't mean it's fabricated." A spokeswoman said O'Reilly thinks that something happened, but is not sure exactly what.
A few days later, Rep. Michele Bachmann, R-Minn., told an audience, "No witness saw it, it's not on camera, it's not on audio."
Only 22 seconds of video have emerged from the time in question, filmed by Lee Fang of the liberal American Progress think tank. His YouTube clip - labeled as being filmed about five minutes after the crowd rushed Lewis and Carson - has been posted by Breitbart and dozens of blogs accusing Democrats of lying.
Fang told the AP he was standing "pretty far away" across Independence Avenue from the Cannon building when he saw the crowd erupt, so he hurried over. Fang did not hear the epithet, but he said he believes it was used. "The hatred was palpable," he said.
Conservatives insist the absence of racial epithets on Fang's video and the 48-second clip show there was no hate.
"If it didn't happen on YouTube," says a regretful Fang, "it didn't happen at all."