This morning, Eli posted a great Obama attack ad accusing Mitt Romney of taking part in the Son of Boss tax scam. CNN published an explanation of what Son of Boss is. Here's a taste:

Romney has had a close, long-standing, personal and business connection with Marriott International and its founders. He served as a member of the Marriott board of directors for many years. From 1993 to 1998, Romney was the head of the audit committee of the Marriott board.

During that period, Marriott engaged in a series of complex and high-profile maneuvers, including "Son of Boss," a notoriously abusive prepackaged tax shelter that investment banks and accounting firms marketed to corporations such as Marriott. In this respect, Marriott was in the vanguard of a then-emerging corporate tax shelter bubble that substantially undermined the entire corporate tax system.

Son of Boss and its related shelters represented perhaps the largest tax avoidance scheme in history, costing the U.S. many billions in lost corporate tax revenues...In his key role as chairman of the Marriott board's audit committee, Romney approved the firm's reporting of fictional tax losses exceeding $70 million generated by its Son of Boss transaction. His endorsement of this stratagem provides insight into Romney's professional ethics and attitude toward tax compliance obligations.

You really should go read the whole thing. Here's the nutshell: You know when people complain about corporations finding tax loopholes that allow them to make billions and not have to pay taxes on the profits? It looks like Mitt Romney is the guy who perfected that system in the 1990s. Is it any wonder that Goldman Sachs is pumping money into Romney's campaign?