Byron York

The second objection is that 9-9-9 would add a national sales tax on top of current income and business taxes, and would thus give Congress another tax to raise. Why couldn't 9-9-9 become 12-12-12? Or 15-15-15? The rates would still seem fairly low. "In the long run it leaves the door open for politicians with the wrong motives to push it upwards, and then we're stuck with something worse than what we had before," says a second expert.

"All taxes over time tend to rise to their highest sustainable point," says a third expert. "So one of the general things you don't want to do, if you're concerned about limiting the size of government, is to introduce a whole new type of tax on top of the current structure."

Lowrie rejects the argument. First, he points out that 9-9-9 would eliminate some major taxes, like the payroll tax. As for the sales tax, he argues that some politicians will always want to raise taxes, and "I don't think they would be any more likely to raise this." Finally, he believes that citizens' movements like the tea party will keep up the pressure against tax increases. Still, the fact remains that under 9-9-9, there would be a new tax on top of existing taxes.

Recently Cain's team came to Washington to explain the plan to conservative economic analysts at Americans for Tax Reform, Club for Growth and other institutions. Those experts are starting from scratch; they haven't really seen anything like Cain's plan before. And for all the problems they have with it -- they're also flummoxed by Cain's inclusion of "empowerment zones" for inner cities -- they still admire Cain for trying to find a new solution to today's problems.

"It's not an entirely coherent set of proposals," says a fourth expert. "I do worry about the end game. But I hate to rain on it because there's no perfect tax system in the world, and this is another person stirring the tax reform debate, and that's a good debate to have."

Byron York

Byron York, chief political correspondent for The Washington Examiner