How does Reid demonstrate that it's true?
This is why it's such a bad idea for Romney not to release his tax returns. It's dirty politics, but if I were the Democrats I would be starting rumors left and right about various awful things that they 'heard' were in them. Once again, the only rational reason for Romney to be fighting this so hard is that there really are things in there that would be very damaging to him if they were to come out.
While I find it highly unlikely that Romney paid zero in taxes over 10 years, it wouldn't be too much of a stretch to find several years in there where he perhaps paid none, or at least paid an extraordinarily low rate. Mitt Romney is defined as a politician by his almost complete lack of principles. Would anyone be that shocked to find that translated over to his personal finances as well?