I didn't say he did anything illegal, but I said he might have, and I think that is a reasonable possibility. We don't know what he is hiding, but whatever it is, it is worth being criticized, worth the damage to his image, and credibility, and respect of many Americans, including in his own party.
So what is it? There are lots of complex tax laws that could be interpreted wrongly, even by experts, unintentionally. Maybe he didn't do anything illegal, but he lied in his speeches about where his money comes from, how he got it, who he damaged to get it etc. Maybe it will show how he uses overseas accounts to dodge taxes, which may be legal, but may not be looked apon as favorably as a regular tax loophole to the American people. I have no problem speculating about all kinds of bad things Romney might have done. That is price he has chosen to pay for not disclosing. The imagination of the people is usually worse than the actual truth, but he apparently doesn't see it that way.
I never said his return is too complex to audit. Are you twisting my words now for lack of a better case?
I said (read slowly)
If that's still to complicated for you I'll simplify. Your "common sense" assumption that the IRS already looked at his returns and would have found any problems with them is incorrect. The IRS never looks at most returns.