Cannon's campaign says they had no idea that the young man they hired to put up lawn signs was also running the Web site.
"There is absolutely no connection between that Web site and the fact that he was paid by us," said Cannon spokesman Joe Hunter.
The site, thetruthaboutjason.com, was taken down this week after inquiries from The Salt Lake Tribune.
The staffer behind the Web site is Jason Smith, who had worked for Republican challenger David Leavitt before Leavitt was eliminated at the Utah Republican Convention in early May. The Web site appeared on May 11, accusing Chaffetz of lying about his views on immigration and about Leavitt's record. The site's comments section included salacious rumors about Chaffetz and attacks on his qualifications, most of them posted anonymously.
Smith told The Tribune last month that the site was his own work and not affiliated with the Cannon campaign.
But Cannon's recent financial disclosure form lists a $500 payment to Smith for "salary."
"The campaign did not know at the time, when we was brought on after the conventions, that he was the one who put the Web site up," said Joe Hunter, a Cannon spokesman.
When the campaign learned that he was behind the site, Smith was asked not to add any more material to it. After he did - his last post was June 8 - the campaign asked him to take it down, Hunter said.
There would be nothing wrong with Smith doing the Web site, Hunter said, but the campaign was concerned about the perception.
Chaffetz said he had seen the site and didn't know who was behind it. But he doubts the Cannon campaign's denials of involvement and said it is the kind of politics citizens are fed up with.
"Being on the receiving end it seemed very calculated to me. I don't mind there being a 'Truth About Jason' Web site, but I didn't see much truth on it," he said. "You're either responsible for what you do or you're irresponsible."
Kirk Jowers, a campaign finance lawyer and director of the Hinckley Institute of Politics, said it would be difficult to prove the Cannon campaign violated campaign finance law.
Federal Election Commission rules don't put limits on volunteer bloggers as long as it is not coordinated or paid for by the campaign.
There may be some perception problems for Cannon, Jowers said, but it is unlikely since the Web site wasn't widely viewed.