President Trump’s dalliance with leftist economic policies appears to be waxing, at least if his telephone call today with Senator Elizabeth Warren is any guide. Mr. Trump, it seems, in an attempt to address the crisis of affordability, is increasingly turning to the palliatives pushed by the Massachusetts Marxist. Mr. Trump’s latest demarche from the Warren playbook is a demand to cap the rates of interest that credit card companies can charge their customers.

Mr. Trump had earlier parroted Ms. Warren’s call to ban investors from buying homes. He is seeking, too, to ban defense contractors from paying out dividends. All this at a time when, thanks to Mayor Zohran Mamdani and his leftist camarilla, private property rights are under a cloud at New York City. It’s “hardly encouraging,” these columns lamented, to witness the emergence of what we called a “Trump-Warren Economic Strategy.”

Meddling in the free market, we cautioned, is no way to foster robust economic growth, even if it might prove temporarily gratifying — say, in the lead-up to midterm elections that seem to have Mr. Trump spooked. That logic informs his announcement on Truth Social that “we will no longer let the American Public be ‘ripped off’ by Credit Card Companies.” He scolds the companies for charging interest rates of 20 percent to 30 percent, or more.

Mr. Trump’s proposed fix — effective January 20, he avers — is “a one year cap on Credit Card Interest Rates of 10%.” Like landlords and bill collectors, one imagines, credit card companies make for easy targets in Ms. Warren’s style of populist demagoguery. This attempt to, in effect, set prices, though, traverses the principle that the invisible hand of the free market offers the most efficient means of allocating resources in a capitalist economy. 

Economist Veronique de Rugy — whose column appears in the Sun — has been alert in recent years to the danger posed by the GOP’s tilt toward populism. She cautions that “price controls of all sorts are disastrous.” The reason why credit card interest rates are so high, she explains, is that “unsecured consumer lending is very risky.” The high interest rate represents “the price for the lender taking a chance on a person.”

That’s why the Trump-Warren stratagem on interest rate caps could actually backfire on the struggling Americans that the policy is meant to help. “If the government artificially caps rates far below the market rate,” per Ms. de Rugy, “banks will stop lending to riskier borrowers.” In her telling, it’s not just “broke shopaholics” who will pay the price, but “the working single parent using a financial last resort before payday,” too.

The interest caps are akin to rent control policies, Ms. de Rugy adds, which “can create a housing shortage by reducing the attractiveness of supplying those homes.” Yet after Mr. Trump’s Oval Office photo-op with Mr. Mamdani, one wonders if the president will be adopting planks from the mayor’s collectivist agenda, too. It’s not hard to imagine, at this point, a Truth Social post echoing Mr. Mamdani’s call to “freeze the rent,” nationwide.  

Which brings us back to Ms. Warren, who is crowing about her call with Mr. Trump. “I told him that Congress can pass legislation to cap credit card rates if he will actually fight for it,” she says. Mr. Trump and the GOP will want to tread warily. The burgeoning policy partnership between Ms. Warren and Mr. Trump might bolster the so-called neo-populists on the right — and left — but the ultimate loser will be America’s system of free enterprise.