Above is a clip of Steve Schmidt from The Last Word answering questions, sort of, about Willard Romney's tax returns. He managed John McCain’s presidential 2008 campaign back when they had access to years and years worth of the potential running mate's tax records.
Via Businessweek.com, Joshua Green offers pure speculation after discussing the matter with some (non-Bain) private equity executives. He believes the 2009 returns are "singularly important":
[Romney] suffered a large enough capital loss [in 2008] that, carried forward and coupled with his various offshore tax havens, he wound up paying no U.S. federal taxes at all in 2009. If true, this would be politically deadly for him. Even assuming that his return was thoroughly clean and legal—a safe assumption, it seems to me—the fallout would dwarf the controversy that attended the news that Romney had paid a tax rate of just 14 percent in 2010 and that estimated he’d pay a similar rate in 2011.
Interestingly, over at CNN, McCain got a little testy when asked if he "could vouch for the fact that Romney had paid taxes and didn't hide his money from taxes offshore... McCain reacted strongly but didn't directly answer the question":
"I can personally vouch for the fact that there was nothing in his tax return that would in anyway be disqualifying for him to be a candidate. Okay?... We're getting into areas now that are improper for me to talk about. Because when people gave us all those records we agreed to confidentiality. The only reason I'm saying what I'm saying now is because of the scurrilous, scurrilous Chicago style sleaze intimations with no basis in fact that there might have been something wrong with his tax returns, which is disgraceful."
Asked again if he knew if Romney had in fact paid taxes over the years, McCain responded, "Oh please. I am not going to get into that kind of conversation. All I can tell you, and I will tell you again, there was nothing disqualifying in his tax returns. And that is a fact."
Got it. Nothing disqualifying, but plenty to hide.