Rep. Barney Frank (D-Mass.) said that vice presidential nominee Paul Ryan's "lack of specifics" about Mitt Romney's tax plan during Thursday night's debate shows that the numbers don't add up.

"You cannot reduce rates that they're talking about and make that up by closing loopholes without hitting some loopholes that are very popular," Frank told The Huffington Post, citing the mortgage interest deduction and other deductions. "His failure to cite those is an admission there is no real way to do that."

Romney has promised to slash marginal tax rates by 20 percent, cut corporate tax rates, and cut taxes on investment income. He has said he will close loopholes to pay for those tax cuts, but he has not specified any major loopholes that he would close.

In the vice presidential debate, Ryan also failed to specify the loopholes that he and Romney would close. Vice President Joe Biden hammered him for his lack of specificity, saying, "The only way you can find $5 trillion in loopholes is cut the mortgage deduction for middle-class people, cut the health care deduction ... take away their ability to get a tax break to send their kids to college."

The Tax Policy Center concluded in a recent study that Romney's tax plan is mathematically impossible without raising taxes on the middle class.

Frank told The Huffington Post that Romney and Ryan are using the deficit as a red herring for their plan to "savage all the domestic programs."

"His main goal wasn't to cut the deficit," Frank said, adding that Romney and Ryan's proclaimed obsession with deficit reduction is "just a way for them to cut back on programs that they don't like, that are too popular for them to cut back on their own without saying we need to reduce the deficit."

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