The major news out of Mark Halperin and John Heilemann's Double Down is that Obama considered dumping Biden as vice-president, but the book also solves one of the 2012 presidential campaign's biggest mysteries: Who told Harry Reid that Mitt Romney paid “basically” no taxes for a decade.

According to a New York Times article about the book, Reid's source was Jon Huntsman Sr., the billionaire father of failed Republican presidential candidate Jon Huntsman Jr. Though interesting, the revelation is not a complete surprise.

Last year, one of Harry Reid's aides said the source was a Republican with connections Romney's Bain Capital, a description that matches Huntsman, who is partners with longtime Bain managing director Robert Gay. For his part, Huntsman Sr., denied the rumors last year, though he did so in a way that basically shit all over Romney:

“I feel very badly that Mitt won’t release his taxes and won’t be fair with the American people,” Huntsman told me. In a reference to Romney’s father, who pioneered the release of returns as a presidential candidate, Huntsman said: “I loved George. He always said, pay your taxes for at least 10 or 12 years.”

“Mr. Romney ought to square with the American people and release his taxes like any other candidate,” Huntsman said. “I’ve supported Mitt all along. I wish him well. But I do think he should release his income taxes."

As for Biden, top Obama aides reportedly considered replacing him with Hillary Clinton because, as the Times put it, the gaffe-prone veep “seemed overly concerned with his own future.” The plan was abandoned when the aides realized the change would not give Obama a significant-enough boost in the polls.

“When the research came back near the end of the year, it suggested that adding Clinton to the ticket wouldn’t materially improve Obama’s odds,” the authors write in their sequel to “Game Change,” which chronicled the 2008 campaign. “Biden had dodged a bullet he never saw coming — and never would know anything about, if the Obamans could keep a secret.”

Other tidbits from the book:

  • Chris Christie was considered as Romney's vice-presidential candidate but wasn't chosen because of concerns about his background and health. “The dossier on the Garden State governor’s background was littered with potential land mines,” Halperin and Heilemann wrote, referencing Christie's refusal to disclose information about a defamation lawsuit, a Securities and Exchange Commission settlement involving his brother, the names and documentation of his household help, information from his time as a securities industry lobbyist, and his medical history.
  • Prior to the 2012 campaign, President Obama found Bill Clinton difficult to be around. “‘I like him ... in doses,’ ” Obama told an aide, according to the book, though the two presidents' relationship reportedly warmed during the campaign.
  • President Obama has little patience for important Democratic donors. After a meeting with George Soros, Obama vowed never to see the billionaire again “if we don’t get anything out of him.”
  • Jon Huntsman Jr. misled Obama aides, assuring them multiple times he would not run for president, even as he was privately meeting with advisors to discuss campaign strategies as far back as Christmas 2010.

[Image via AP]