As Herman Cain’s poll numbers have vaulted him into the top ranks of the potential Republican nominees, his 9-9-9 plan for taxation is getting new attention. It’s politically potent, because it’s easy for the average voter to get a handle on and, well, it’s a plan. None of the other candidates have one, just political bomfog about being in favor of tax reform, a nip here and a tuck there for the current tax code. But as I suspect the people know and the chattering classes don’t want to know, the tax code cannot be reformed. Any changes just add to its monstrous and deeply corrupt complexity. It will be a dead weight on the American economy until it is replaced with a brand new tax system.

The first phase of the 9-9-9 plan would lay a 9-percent flat income tax on both corporations and individuals, with only a charitable-donation deduction beyond the personal deduction in the latter. It would also institute a 9 percent sales tax on all goods and services. It would eliminate capital gains taxes, double taxation of dividends (they’d be a deduction against corporate income taxes), and the payroll tax. There would be additional tax goodies for businesses and people living in certain “empowerment zones,” presumably areas of high unemployment and low incomes. The second phase would be simply a “fair tax”—i.e. a national sales tax high enough to replace the corporate and personal income taxes. In other words, the 9-9-9 plan would phase into a TK plan. Just replace the TK—a strange editorial term for “to come”—with whatever number would work. Unfortunately, there is not an economist in the world who could tell us what that number should be.

I’m all for flat income taxes. They are simple, fair, and inescapably progressive. Warren Buffett should love the flat tax, as it guarantees that he pays a higher effective tax rate than his famously overtaxed secretary. But the sales tax is not progressive. Instead, it is inescapably regressive. The higher a percentage of a person’s income is spent every year, the higher percentage of his income is taxed away. And the less well-off spend a much higher percentage of their incomes than do the more well-off. Warren Buffett’s notoriously modest lifestyle would allow him to go almost wholly untaxed in a tax system that relied entirely on a sales tax. Even the very rich who indulge in multiple homes, yachts, private jets, and caviar washed down with Château d’Yquem at every meal, bank the vast majority of their incomes and thus would escape the sales tax on most of it. One can eat only so much caviar after all.

So Herman Cain has a plan, which is more than can be said for his competitors for the nomination, and it has a catchy and politically useful name. Unfortunately, it’s not a good or a practical plan. But if it forces the other candidates to develop plans of their own that can then be debated, it will have done good service.