The speech that caught our attention at the Conservative Political Action Conference this year is the one delivered Saturday by President Javier Milei of Argentina. It’s an eloquent warning against socialism from a country that has suffered under it for decades. Mr. Milei spoke of Austrian economists, such as Hayek, Rothbard, and others, and shunned ad hominem attacks, instead speaking of ideas. It couldn’t have been more apropos the moment.

Blamed if it wasn’t a refreshing moment, too. Let’s hope President Trump was listening. While Mr. Trump spoke darkly of a “judgment day” on November 5, casting himself as a “dissident” and warning of “revenge,” Mr. Milei appeared as a happy warrior, introducing himself as a libertarian “lion.” He put forward what he called a “message of optimism,” noting how Argentina had “seemed to be a country condemned to be like sheep, driven by socialists.”

So when he began his political career in Congress, he added, he made it clear “I wasn’t there to herd sheep but rather to awaken lions, and we continue to awaken more and more lions every day.” He explained how Argentina’s political “caste,” who “put their privileges above the welfare of Argentines,” had led what was once among the world’s wealthiest nations into the ditch of inflation and poverty — afflicting, a new study says, 57 percent of the country.

That stunning statistic underscores the extent of the job Mr. Milei has ahead of him — and, as his remarks underscored, the fact that it was the result of Argentina’s embrace of Perónism, a mix of statism and nationalism. “None of the varieties of socialism can work,” is how Mr. Milei put it. Hence, he warned, “don’t let socialism advance, don’t endorse regulation, don’t endorse the idea of market failure,” and “don’t let the siren calls of social justice fool you.”

Mr. Milei told CPAC, “I come from a country that bought all of those stupid ideas.” As a result, he lamented, Argentina went “from being one of the most affluent countries in the world,” and “now we’re ranked 140.” That animates his ambitious agenda to, as he put it, “give Argentines more freedom and to eliminate corruption from politics.” The program, which guts job- and growth-killing regulations, faces uncertain prospects in Argentina’s Congress.

Mr. Milei marks that his reforms are being “met with resistance” from what he calls the current “beneficiaries of this system.” This includes members of “the corrupt caste,” he averred, and “trade unionists who take care of their business, against the people.” That’s a reference to the leftist labor movement that is trying to derail his agenda with strikes. Despite the opposition, he vowed “we are not going to give up on making Argentina great again.”

The best part of Mr. Milei is that he thinks like an economist. The last president we encountered who did that was President Reagan. CPAC was no doubt looking for a barnburner, but Mr. Milei gave them the hay and he put it down to where us mules can get to it. All while referring to the giants like Hayek and explicating the inherent contradictions of socialism that make it inevitably an enemy of freedom and prosperity.

In an illuminating vignette Mr. Milei related how, when Edison invented the light bulb, it hurt candle makers. If “those who favored intervention” by the state had prevailed then, he warned, the government would have propped up the candle makers and stifled the new innovation. So, he went on, “instead of having this conference in this lovely venue today full of light we would still have candles.” That, he explained, is “how socialists mess up our lives.”

We’d like to think the economist-president’s warning against any “distortion” of the free market could serve as an antidote for those on the neo-populist right who are showing a newfound fondness for government regulation and subsidies — when such measures appear to advance conservative goals. “Don’t surrender your liberty, fight for your freedom,” the Lion of Argentina roars. “If you don’t fight for your freedom they will drag you into misery.”