McCain's website says that he will propose a new, alternative tax system, adding, "When this reform is enacted, all who wish to stay under the current system could still do so, but everyone else could choose a vastly less complicated system with two tax rates and a generous standard deduction."

That makes it sound as though McCain is planning to go with some version of the tax-reform proposal that such conservative stalwarts as Rep. Paul Ryan, former presidential candidate Fred Thompson, and the Republican Study Committee have been promoting over the last year. That proposal has many good points. It brings the top tax rate way down to 25 percent (from the current 35).

But the combination of the low rates, the elimination of the AMT, and the introduction of a choice of tax codes for taxpayers would yield a big revenue hit for the government. To advocate it honestly, McCain would either have to abandon his concern about the deficit or specify many more budget cuts than he has so far. Worse, the alternative, reformed code achieves its low rates in part by scaling back the tax credit for children. The tax burden would be reduced, but families would be paying a larger share of it. Does McCain really want to campaign on a platform of shifting the tax burden from corporations to families?

An Alternative Alternative

It may seem impossible for a tax reform to have all the qualities that McCain should be looking for: one that simplifies the code, levies only

A vastly expanded child tax credit, applicable against both income and payroll taxes, would reduce the tax burden quite a bit for lower middle class families. To promote growth, the reform could keep taxes on investment low while modestly reducing the top marginal tax rate. To take in as much money as the current tax code, meanwhile, this reformed, pro-family system would have to do two main things. First, it would eliminate or at least cap the deduction for state and local taxes. Second, its top rate, though lower than the current one, would apply to a lot more people.

The big winners from the Thompson/RSC proposal--the people for whom McCain would be taking significant political risks--would be affluent, childless households in high-tax states. The AMT, which has hit more and more of these households because it does not allow a deduction for state and local taxes, would be gone. Their tax rates would go down. And they don't take the child tax credit as it is. These same households would lose money under the pro-family reform. Their marginal tax rate would go down, but it would apply to a larger share of their income, and they would not be able to deduct as much of their state and local taxes.

In 1980, 1988, and 2000, Republicans won presidential elections in part by promising to tax a lot of middle-income voters significantly less than the Democrats would. If McCain wins this election without making such a promise, he will be the first Republican to do so in more than three decades. Or he can embrace a pro-family plan, and thereby go a long way to showing that he intends to reform our institutions to facilitate the pursuit of the American dream.

Ramesh Ponnuru is a senior editor at National Review.