Heh.

Romney’s answer won’t satisfy everyone. (More on that below.) But, in asserting that for the last decade he has never paid less than a 13 percent tax rate, Romney is calling Democrats’ bluff and forcing them now to call him a liar if they argue that he paid any less. In short: The burden of proof has now shifted from Romney to Senate Majority Leader Harry Reid and the Democratic party more broadly.

WaPo forgot the ‘proof’ part of ‘burden of proof’.