According to Giuliani spokeswoman Sunny Mindel, the plan was stolen from an aide's suitcase last fall, photocopied, and then returned to the aide's suitcase.
"This is clearly a dirty trick," Mindel told the New York Daily News. "The voters are sick and tired of this kind of thing."
The document was given to the Daily News, which published a story about the Giuliani plan on Tuesday. The newspaper said it obtained the document from a source sympathetic to one of Giuliani's presidential rivals.
The source said the plan had been left behind in one of the cities where Giuliani campaigned for GOP candidates prior to the November 2006 election.
The campaign blueprint includes a plan to raise at least $100 million in 2007 getting the support of major GOP donors like Lew Eisenberg and Larry Bathgate, both from New Jersey, and Fred Smith, the CEO of FedEx, the paper reported. Those three are already supporting Sen. John McCain's bid.
The document also predicts some $100 million could be spent against Giuliani to highlight political vulnerabilities like his three marriages, his support for disgraced former aide Bernard Kerik and his moderate position on social issues, such as abortion, gun control and gay rights.
Mindel downplayed the importance of the plan, saying it was "simply someone's ideas which were committed to paper over three months ago."
Since stepping down as mayor of New York, Giuliani has built a thriving business as a security consultant. An adviser to one of Giuliani's potential GOP presidential rivals -- Sen. John McCain -- was quick to point out the embarrassment losing such a document might produce.
"I'm surprised that something like that would ever leave the custody of a campaign, and that such raw and frank information would be around the countryside," McCain adviser John Weaver told the New York Times.
Giuliani is a hugely popular fundraiser for his party, due largely to his response to the terrorist attacks of Sept. 11, 2001, for which he was dubbed "America's Mayor." He leads McCain in most polls.
Mindel told the Times she did not know whether Giuliani would seek a criminal investigation into the alleged theft.