Via David Graham, Romney offers the following rebuttal on his taxes:

I just have to say, given the challenges that America faces -- 23 million people out of work, Iran about to become nuclear, one out of six Americans in poverty -- the fascination with my taxes I find to be very small-minded. I did go back and look at my taxes and over the last 10 year I never paid less than 13 percent. I think the most recent year is 13.6 percent or something like that. I paid taxes every single year. Harry Reid's charge is totally false. I'm sure waiting for Harry to put up who it was that told him what he says they told him. I don't believe it for a minute by the way. Every year I've paid at least 13 percent, and if you add in addition the amount that goes to charity, why, the number gets well above 20 percent.

...Romney pays a lower effective tax rate than 60 percent of Americans, and those who pay lower are the poorest 40 percent of the population. And that shows Romney's trouble, and why his answer is a bit disingenuous. For example: Mitt Romney mentioned in that very statement that he wants to stop Iran from becoming nuclear, and he wants to expand the defense budget, and that requires money. Meanwhile, Romney has voiced support for reforms proposed by his running mate Paul Ryan that would reduce federal spending on entitlements. Federal revenues matter to those things. While the amount Romney is paying to the IRS every year isn't the difference between solvency and not, it's not hard to see why people care about what wealthy people like him are paying.