Romney's basic idea, which in broad outline has bipartisan support, is to "lower tax rates" and "broaden the base" by reducing deductions, credits and exemptions. He proposes cutting individual income tax rates by 20 percent, so that the top rate would be 28 percent rather than the current 35 percent and the bottom rate would drop from 10 percent to 8 percent. He also wants to abolish the estate tax, repeal the alternative minimum tax, and eliminate taxes on interest, dividends and capital gains for taxpayers earning less than $200,000.
Since Romney insists "there'll be no tax cut that adds to the deficit," he needs to make up for the lost revenue by cutting back on tax breaks, and he is committed to doing so without increasing the burden on "middle-income" households, shrinking the share of taxes paid by "high-income" households or reducing the tax code's incentives for savings and investment. According to a widely cited August report from the Tax Policy Center (TPC), a joint project of the Urban Institute and the Brookings Institution, this task "is not mathematically possible," a point that President Obama emphasized during the debate.
The Romney campaign dismissed the TPC's "biased study," saying it failed to take into account "the positive benefits to economic growth" from his deficit reduction plan and his proposed cut in the corporate income tax. If those changes boost economic output, tax revenue will increase, reducing the amount that needs to be raised by closing loopholes.
As usual, however, Romney did not show his math. He did not even estimate the magnitude of those "positive benefits" (as opposed to negative benefits?) so people could judge whether he was being realistic. More crucially, he has never specified which deductions he would scale back or abolish, and his plan to restrain spending is mostly a mix of penny-ante items (e.g., the $146 million National Endowment for the Arts, which Romney would not even eliminate) and wishful thinking (e.g., $60 billion a year saved by controlling "waste and fraud").