The two campaigns have both made Romney’s tax plan a central part of the campaign so far, with the GOP ticket saying their plan would help spark much-needed economic growth.
In addition to cutting all individual tax rates by 20 percent, Romney has said he wants to eliminate the estate tax and the Alternative Minimum Tax, and at least keep the current preferences for capital gains.
And as Ryan said Thursday, the ticket also says the plan will not add to the deficit nor shift any of the tax burden away from the wealthy.
But the Urban-Brookings Tax Policy Center has said that the tax policies proposed by Romney and Ryan would mean a lower tax bill for those making more than $200,000 a year.
If the plan were to be made revenue-neutral, the center said, that would imply that more middle-class taxpayers would have to pick up the slack.
But Ryan said Thursday that the math would work, citing six separate studies, and that a Romney administration would target tax preferences used by the highest earners. Ryan added that he and Romney wanted to work with lawmakers to find which tax preferences to eliminate.
“It is mathematically possible. It's been done before. It's precisely what we're proposing,” Ryan said.
The seven-term congressman also pointed out that the 1986 tax reform was a bipartisan achievement, pushed through by key figures like President Reagan and a Democratic House Speaker, Tip O’Neill.
“They worked together out of a framework to lower tax rates and broaden the base, and they worked together to fix that,” Ryan said.
But Biden said that Republicans had shown no interest in what he called some of the biggest loopholes, like the current low rate on capital gains and the so-called carried interest break used by hedge fund managers.
“You think these guys are going to go out there and cut those loopholes?” he asked.