Senate Majority Leader Harry Reid’s allegation that Mitt Romney hadn’t paid taxes in a decade came from Jon Hunstman Sr., a new book on the 2012 presidential campaign claims.

“Double Down: Game Change 2012” is a behind-the-scenes account of the election by political reporters Mark Halperin and John Heilemann. In a section of the book, long time Romney backer Huntsman is attributed as Reid’s source.

Huntsman is the father of one of Romney’s rivals, former Utah governer Jon Huntsman Jr. He was suspected by some to be Reid’s source, though he denied being the source when questioned by the Washington Post’s Greg Sargent.

In a July 2012 interview, Reid claimed a Bain Capital investor had tipped him off to the governor’s negligent tax paying. He stood by the claim throughout the entire campaign.

Both Reid and Huntsman pressed Romney to release his tax information to the public.

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

The book also includes how the Obama campaign secretly considered replacing Joe Biden with Hillary Clinton on the 2012 ticket. According to some White House staffers, Joe Biden was too consumed with his own political future.

Sources: The Huffington Post, The Atlantic Wire