The source behind Senate Majority Leader Harry Reid's (D-Nev.) bold claim that Republican presidential candidate Mitt Romney had paid "basically" no taxes for a decade was Jon Huntsman Sr., a new book on the 2012 campaign claims.

The New York Times on Thursday offered details from "Double Down: Game Change 2012," a behind-the-scenes account of the election by political reporters Mark Halperin and John Heilemann. Among the nuggets in the book is the reveal that Reid's source was Huntsman, a longtime backer of Romney.

In a July 2012 interview with The Huffington Post, Reid said a Bain Capital investor had told him that the former Massachusetts governor "didn't pay any taxes for 10 years."

"He didn't pay taxes for 10 years! Now, do I know that that's true? Well, I'm not certain," Reid said. "But obviously he can't release those tax returns. How would it look?"

Reid stood by the claim throughout the campaign.

Huntsman Sr., the father of one of Romney's primary rivals, former Utah governor Jon Huntsman Jr., was suspected by some to be Reid's source. While Huntsman Sr. denied to the Washington Post's Greg Sargent that he was behind the tax delinquency rumors, he pressed Romney to release his returns to clear the air.

“I feel very badly that Mitt won’t release his taxes and won’t be fair with the American people,” he said.

The upcoming book also offers unflattering details on Huntsman Jr.'s presidential bid. The Times' Jonathan Martin reports:

As Mr. Obama’s ambassador to China, he repeatedly assured top White House officials that he was not considering a Republican presidential bid, even as he was meeting with potential campaign strategists during a trip to his Washington home around Christmas 2011. And while Mr. Huntsman was in Beijing, his wife was exchanging emails with his eventual consultant, trying to be discreet about their political plans by referring to her husband only with the code word “HE.”

UPDATE -- 3:41 p.m.: Huntsman denied he was the source of Reid's information in an interview with the Salt Lake Tribune.

"It’s so ridiculous that people associate my name with Mitt Romney’s tax returns, like I would have interest in it or know about it," Huntsman told The Salt Lake Tribune. "These fellows who wrote this book, they dwell on falsehoods and false rumors. They’re nothing but supermarket, tabloid trash. They ought to be ashamed of themselves."

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