Philip de Vellis, a strategist with Blue State Digital, acknowledged in an interview with The Associated Press that he was the creator of the video, which portrayed Clinton as a Big Brother figure and urged support for Obama's presidential campaign.
De Vellis, 33, said he resigned from the firm on Wednesday after he learned that he was about to be unmasked by the HuffingtonPost.com., a liberal news and opinion Internet site.
Blue State designed Obama's Web site and one of the firm's founding members, Joe Rospars, took a leave from the company to work as Obama's director of new media. The connection to the campaign is likely to be a setback for Obama, who has cultivated an image as politician who wants to rise above bare-knuckle politics.
"It's true ... yeah, it's me," de Vellis said Wednesday evening.
He said he produced the ad outside of work and that neither Blue State nor the Obama campaign was aware of his role in the ad.
"But it raises some eyebrows, so I thought it best that I resign and not put them in that position."
Thomas Gensemer, the managing director of Blue State Digital, said de Vellis was fired.
"Mr. de Vellis created this video on his own time," Gensemer said in a statement. "It was done without the knowledge of management, and was in no way tied to his work at the firm or our formal engagement (on technology pursuits) with the Obama campaign."
In its own statement, the Obama camp said the campaign "had no knowledge and had nothing to do with the creation of the ad.
"Blue State Digital has separated ties with this individual and we have been assured he did no work on our campaign's account."
The Clinton campaign had no immediate comment.
In the interview, and later in a blog written for the Huffington Post, de Vellis expressed pride in his creation, while acknowledging that his employers are "disappointed and angry at me, and deservedly so."
"It changes the trajectory of my career," he said.
In his blog posting, he wrote: "I support Senator Obama. I hope he wins the primary. (I recognize that this ad is not his style of politics). I also believe that Senator Clinton is a great public servant, and if she should win the nomination, I would support her and wish her all the best."
The ad was guerrilla politics at its cleverest and had become the boffo hit of the YouTube Web site.
The 74-second clip, a copy of a 1984 Apple ad for its Macintosh computer, has recorded nearly 1.5 million views, with an enormous surge in the past two days. The video's final image reads "BarackObama.com."
The ad was originally posted by "ParkRidge47" – presumably referring to the Chicago suburb and year in which Sen. Clinton was born, reports CBS News correspondent Richard Schlesinger.
De Vellis remained hidden for weeks, protected by the anonymity afforded by YouTube and the absence of federal regulations governing most Internet political speech.
The ad portrayed Clinton on a huge television screen addressing robotic humans in a stark, futuristic hall. A female athlete tosses a hammer at the screen, destroying Clinton's image with an explosive flash. Then this text: "On January 14th the Democratic primary will begin. And you will see why 2008 isn't going to be like '1984."'
De Vellis said he used footage of an updated Apple ad that portrayed the female athlete wearing an iPod. He said he used standard Apple equipment to modify the video and edit Clinton's image into the clip.
Obama, appearing on CNN's "Larry King Live" Monday night, said his campaign knew nothing about the origins of the anti-Clinton ad.
"Frankly, given what it looks like, we don't have the technical capacity to create something like this," he said. "It's pretty extraordinary."
De Vellis said he is an Obama supporter who was inspired to do the ad after he read reports that Clinton backers were "strong-arming" Democrats for money and support.
He added: "I didn't really like the style of some of Senator Cinton's videos and the way they were presenting her on the Internet. I just thought it was little bit disingenuous."
Still, he said, he was stunned by the reaction to the video.
"This blew up much much more than I ever thought it would," he said. "I want to make it clear that I don't think that Hillary Clinton is Big Brother or a bad person or anything."