For example they describe in detail the tax mix e.g. income versus capital gains, as well as the nature of liquid assets, deduction types etc.
But we would probably learn something like:
a) he's not nearly as rich as he claims
b) he's made maybe $50M this year and paid $0 in taxes due to write-offs in earlier years.
That would not go down well publicly.
Romney paid an effective rate of 14% on his $500K income (I think all capital gains) and that was destructive for his campaign. It just looks pretty out of touch - 99% of Americans earn less than $500K and pay far more than 14% in taxes.
So it would have been a publicity disaster, enough to hurt him badly.
Maybe some other skeletons in there.
But I don't think anything illegal.
Mitt Romney and his wife, Ann, paid $1.94 million in federal taxes on last year's income of $13.7 million, for an effective tax rate of 14.1 percent, his campaign said Friday.
http://www2.ljworld.com/news/2012/sep/21/romneys-paid-194-mi...
He also gave $4 million to charities.
Somehow everybody always forgets this part - when you donate to charity, this is deduced from the taxable income, usually, but is not accounted for in tax rate calculation. Which means, if I earned tons of money and donated it all to charity - I'd pay 0% taxes, so people would say "why this fatcat doesn't pay any taxes even though we are paying a lot, he must be doing some shady things!".
I think he'd just come off as an every-day man-of-the-people who understands the economic fears of rural whites but also a savvy businessman who's too smart to pay taxes like a sucker.
