The mechanics of the choice are an important detail that will determine the revenue estimate and economic effects of the proposal, said Douglas Holtz-Eakin, a former director of the Congressional Budget Office who advised Republican presidential candidate John McCain in 2008.
"If you let people go back and forth, you give up a lot of those efficiency gains," he said.
Choice Of Systems
Under the choice offered by Perry, taxpayers will gravitate to the system that gives them the most benefits, Norquist said. Perry's proposal doesn't punish people who have organized their financial lives around tax breaks such as the mortgage interest deduction or the earned income tax credit, he said.
"It just strikes me as political pandering at its worst," said Leonard Burman, a former Treasury Department official who now teaches at Syracuse University in New York. "It doesn't seem like a serious policy proposal."
Low-income taxpayers, who benefit from refundable tax credits for work and children that generate benefits in excess of their tax liability, might prefer the existing system. So would many middle-income taxpayers. The current top marginal rate doesn't exceed 15 percent until taxable income reaches $34,500 a year for individuals and $69,000 for married couples.
Perry, who has described himself as "dismayed at the injustice" that nearly half of households don't pay federal income taxes, wouldn't change that percentage with his plan, Burman said.
"He may still be dismayed, but he's not going to raise their taxes, because he wants them to vote for him," Burman said.
Wealthy Benefit
Wealthy taxpayers, attracted by the lower rate and the elimination of taxes on capital gains, dividends and estates, likely would migrate to the new system. The top rate on wage income is now 35 percent, and the top tax rate on most long-term capital gains in 15 percent.