That slipperiness is captured in the Democratic National Committee's latest parody website, romneytaxplan.com, which mocks Mitt Romney's tax plan.

A button on the website directs users to "get the details" on how the Romney-Ryan tax plan is "able to cut taxes by $5 trillion without raising taxes on the middle class or exploding deficit," but like a child dodging the enemy in a game of tag, the button slips away every time an attempt is made to press it.

The Romney-Ryan campaign has declined to specify which loopholes and deductions Romney would eliminate to fulfill his pledge to bring tax rates down by 20 percent. The candidates have said that decision is best left for Congress to decide upon.