Supply-side economics works, I tell you! It works! Photo: Scott Eells/Bloomberg via Getty Images

Reducing the top tax rate has been the Republican Party’s highest priority for a quarter century. Since the 2012 election, a handful of apostates have gently urged it to change course. Paul Ryan, who remains the most powerful figure within the party, has just given an interview to John McCormack, and he has a message for the reformers who want to change course: forget it. Ryan, reports McCormack, “made it clear that he disagrees with some conservatives who are willing to accept a high top tax rate in order to increase the child tax credit.”

If the significance of Ryan’s statement here doesn’t immediately strike you, let me explain. Starting in the early 1980s, supply-side economics emerged as the Republican Party’s policy doctrine. Supply-side economics holds that the marginal tax rates hold the key to economic growth, and thus that even tiny changes to tax rates can unleash massive changes to economic performance. Accordingly, Republicans have valued low tax rates over absolutely everything else.

In the 2012 election, that commitment turned into a major liability for the party. The Republican ticket ran on a somewhat sketchily defined plan to reform taxes, the impact of which would have been to give the richest one percent a huge tax cut and impose higher taxes on the middle class.

The Republican reformers have, correctly, identified the commitment to reducing the top tax rate as a major (or even the major) liability. The most important theme of “Room to Grow,” a policy manifesto by “reform conservatives,” is that the GOP should abandon supply-side economics. In some ways, this is the key to many other policy choices the party faces. If they keep their traditional commitment to low top tax rates above all else, there’s simply no money to spend elsewhere. On the other hand, if Republicans stop proposing to cut rich peoples’ taxes by hundreds of billions of dollars, they’ll be able to spread that money around on other things — tax credits for middle-class families, maybe some kind of health insurance — that would benefit a vastly larger bloc of voters. The policy champion for this bloc is Utah Senator Mike Lee, who has at least tried (the math is tricky) to craft a tax-reform plan that would hold taxes for the rich constant while expanding the child tax credit.

The reformists cast their argument in the most soothing possible tones. Cutting marginal tax rates was the correct policy in 1980, they agree. (It is axiomatic among Republicans that everything Ronald Reagan did was correct, even the things that contradicted other things he did.) But the world has changed, tax rates have fallen, and what worked for 1980 does not apply today.

Reaganomics, now and forever, amen. Photo: Ralf-Finn Hestoft/Corbis

With predictable fury, supply-siders have denounced this heresy. You can get a flavor of the intra-party debate in columns appearing in places like Forbes or The Wall Street Journal, the later of which retorts, “Good economic policy doesn’t have a sell-by date. (Adam Smith? Ugh. He is just so 1776.)”

Ryan has positioned himself as a reformist in some ways. He acknowledged that calling people who get government benefits “takers” is mean. On the other hand, Ryan is a longtime, deeply devoted supply-sider. As a teenager, he immersed himself The Way the World Works and Wealth and Poverty, the two foundational texts of the supply-side economics worldview (both of which happen to be barking mad), which teach the absolute primacy of marginal tax rates.

So Ryan is cross-pressured here, between a faction that is attempting to excise the party’s weaknesses and his own most fundamental convictions. His answer to McCormack is surprisingly blunt:

“I’m a classic growth conservative. I believe that the best way to help families, the best way to help the economy is to reduce rates across the board,” Ryan said when asked about Utah senator Mike Lee’s plan to increase the child tax credit and create two income tax brackets of 15 percent and 35 percent. “Growth occurs on the margin, which is a wonky way of saying, if you want faster economic growth, more upward mobility, and faster job creation, lower tax rates across the board is the key—it’s the secret sauce.”

That’s Ryan’s conviction. He disagrees with Lee that subsidizing middle-income families with children ought to be the party’s priority. He still believes marginal tax rates are the “secret sauce.” To Ryan’s credit, in this case, he is not hiding it.