Mitt Romney has a credibility problem. He changes his beliefs like laundry (abortion, medical insurance, whether Bin Laden was worth killing, attacking Iran), refuses to disclose his tax returns, and won't explain how he could possibly pay for the tax cuts he proposes. But there is another scandal in Romney's campaign -- namely Glenn Hubbard, Romney's chief economic advisor, who was chairman of the Council of Economic Advisors under George W. Bush, and is now Dean of Columbia Business School. I interviewed Hubbard for my documentary film Inside Job, and analyzed his record again for my book Predator Nation. The film interview became famous because Hubbard blew his cool after I interrogated him about his conflicts of interest: "This isn't a deposition, sir. I was polite enough to give you time, foolishly I now see, but you have three more minutes. Give it your best shot." But the really important thing about Hubbard isn't his personality; it's that as an economist and an advisor, he is a total, unmitigated disaster.