Both John King and David Gergen have stated that the Democrats have in fact not told the truth about the length of time Romney spent at Bain.
Nobody has any proof whatsoever of any wrongdoing by Romney with his taxes. It wouldn't matter in the least what tax records showed. They would show absolutely nothing wrong, however, Obama and his henchmen would take all this data and find something that they could twist and turn in order to confuse people about Romney's taxes.
Bottom line, smoke screen.
Underlined bottom line, smoke screen because Obama really has no clue what to do about the economy.
I think you'd have found a lot of people who, if Romney released his tax returns and assuming there was nothing illegal (which I doubt there is) or potentially unethical or irregular, would say it's time to let it go.
That's the big problem, which shows how politically tone-deaf and glass jawed his campaign is. They could have been the ones to control the cycle to addressing issues head on, without waffling and stupid lines about 'retroactive retirement'. But instead, Obama is able to suggest that Romney is breaking a precedent set by his own father because of something he doesn't want people to see.
The capacity of whatever tax/Bain attacks to impact on Romney is down his own campaign's incompetence.