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.
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.
