Diana Furchtgott-Roth argues that the Lee-Rubio proposal would be improved if it had three tax brackets instead of two. I don’t think the trade-off is worth it, myself, but her argument is a reasonable one.

Amity Shlaes and Matthew Denhart are more critical of the plan, arguing in the Wall Street Journal that the senators should scrap the child credit and use the money to cut tax rates, especially the top tax rate, further. They cite Dan Mitchell of the Cato Institute for the proposition that moving to a flat tax—which would of course involve a lot more than scrapping the child credit—would bring the top tax rate down below 20 percent.

Lee-Rubio, they say, is in contrast divisive and will breed resentment. “Couples with several children who live in low-tax states with lower-cost housing are entitled to breaks. Couples who live in high-tax states and are childless are not. Businesses enjoy lower rates than wage earners.” (They mean “a minority of wage earners” in that last sentence, by the way.)

I don’t think most people think about tax policy this way. We currently have “tax breaks” for children, health insurance, state and local taxes, mortgage interest, and charitable contributions (scare quotes because, as I’ve argued at length before, the tax break for kids isn’t really a departure in principle from neutral treatment of families by the government). Some of these are worse ideas than others, but they have not, in fact, proven to be divisive or resentment-generating.

Both the Lee-Rubio plan and the flat tax would produce winners and losers. While the Lee-Rubio plan would lower the top marginal tax rate and lower average tax rates, Shlaes and Denhart are right to note that some affluent childless couples in high-tax states would pay more than they do today. That’s an unfortunate feature of the plan in my view, though not one that’s easy to avoid.

Shlaes and Denhart don’t spell out the details of the flat tax they have in mind, but it seems likely to involve higher tax rates and higher tax bills for married couples with less than $75,000 a year in taxable income (especially if they have kids). Getting rid of the tax exclusion for health insurance would hit scores of millions of people, and the payoff for it would be bringing tax rates on people in the top third or so of the income distribution down. Getting rid of the mortgage-interest deduction would have a similar trade-off. All in all, that kind of plan, while it does have its merits, seems like it would generate more than its share of resentment.