[N]one of this appears to add up to 10 years of tax returns with no taxes paid. "It is theoretically possible, but it seems quite improbable in practice given the portfolio in 2010," [law professor Edward] Kleinbard said. "It is improbable that a man of his wealth would have paid no taxes for 10 years..."

Still, Reid claims that Romney did not pay taxes for 10 years. Moreover, he claims to base this on information from a Bain investor, without explaining how someone not intimately familiar with Romney's tax situation would know details of his taxes.

We asked a Reid spokesman for more backup information and for the name of a tax expert who could back up Reid's claim but did not receive a response.