It was former Utah Gov. Jon Huntsman’s struggling presidential campaign that fed the rumors to the press that Republican presidential candidate Herman Cain had been accused of harassment by multiple women during his business career — a story that ultimately led to Cain’s departure from the contest — a new book reveals.

Cain, the former CEO of Godfather’s Pizza, vehemently denied the claims at the time and shamed Politico, the outlet which eventually wrote about the anonymous accusations, for reporting the story.

But a big mystery since then: who fed Politico the story? Authors John Heilemann and Mark Halperin write in “Double Down: Game Change 2012” that a campaign that no one really expected was behind the oppo on Cain.

“After getting a tip from a donor, Huntsman’s researchers had dug into Cain’s past, discovered the first two sexual harassment claims, and fed the story to Politico,” the book recounts, according to an excerpt in U.S. News and World Report. “As they waited for Politico to turn their tip into a story, members of Huntsman’s circle asked each other when the ‘high heel’ was going to drop on Cain.”

An aide to Cain told The Daily Caller on Monday that the businessman and radio host has yet to read Heilemann and Halperin’s account, which hits bookshelves Tuesday.

The revelation that Huntsman’s campaign was behind the rumors is ironic, considering how the former U.S. Ambassador to China lamented during the episode that the Cain allegations were keeping Republicans from talking about real issues during the campaign.

“Every time another accusation comes up, it diminishes our ability to stay focused on the issues that really do matter for the American people,” Huntsman said in November 2011. “And I think that’s a disservice to the voters.”

Jonathan Martin, the chief Politico reporter on the Cain story who would know the source, did not reference the revelation in his review last week when he broke several juicy nuggets inside the new book for the New York Times.

Follow Alex on Twitter