Yet as president, Mr. Trump has piled on about $3 trillion to the debt, bringing the total to $22.9 trillion. What’s amazing is that he has managed to increase deficits at a time of historically low unemployment and relative peace, when one would expect the national balance sheet to improve.

Republicans are noticeably silent. Whereas the anti-establishment populism of the Tea Party put pressure on Republicans to address the problem, Mr. Trump’s brand of populism has moved the party in the opposite direction. In July, when a caller to Rush Limbaugh expressed concern about the return of $1 trillion deficits under Mr. Trump, the radio host, who has always had his hand on the pulse of his audience, responded: “Nobody is a fiscal conservative anymore. All this talk about concern for the deficit and the budget has been bogus for as long as it’s been around.”

Dismissing fiscal conservatism as a bogus issue is a serious mistake that poses an existential threat to a movement that was built around limiting the burden that government places on individuals. Republicans may convince themselves that they can cut taxes every time they take power, but the reality is that if the long-term debt is not put on a manageable trajectory through reasonable reforms, it will require enormous, crushing tax increases just to sustain existing government programs.