Not since Lincoln and Douglas can we remember a call to a national election debate like that which President Trump has been sounding in respect of socialism. He placed this marker in his State of the Union speech, vowing that America would never be a socialist country. He picked up the theme in his speech at CPAC, offering a taste of how the issue will sound in the campaign now gathering.

The director of the National Economic Council, Lawrence Kudlow, also at CPAC, made a more formal call to a debate. “Our opponents,” he warned, “are proposing to overturn America’s success.” Between the Green New Deal, ending private health insurance, and taxing the rich, Mr. Kudlow reckons, Democrats are proposing essentially “state control — a state government control of the entire economy.”

What Mr. Kudlow asked for in return is a battle of ideas over the Democrats’ socialism. “I want it challenged, I want it debated, I want it rebutted, and I want to convict socialism,” Mr. Kudlow said. To his audience, which included hundreds of activists and members of the conservative intelligentsia, Mr. Kudlow put it this way: “I want you to put socialism on trial. That’s what I’m asking you to do today.”

How we wish Friedrich Hayek were alive for the coming campaign. He wrote, in “The Road to Serfdom,” a template for the debate ahead. Published in 1944, his book illuminates why state control of the economy always leads to a loss of liberty. He helped us see why, as we like to put it, political liberty and economic liberty can’t exist the one without the other. They are but warp and woof in the fabric of freedom.

The importance Hayek attached to debate we glimpsed first hand. On a trip between Hong Kong and New York, we’d stopped off to see him on the Coast (as Sun-style refers to California), where he was spending a semester. We had stopped off to meet him and to ask him about a book we were reviewing on development economics. That turned out to be but the first course.

Hayek, after taking a snort of snuff that might have knocked over a horse, asked if he could tell us about his own project. We were all ears. What was really pre-occupying him, he said, was the idea of a global debate on socialism. This was in the late 1970s, when the Soviet Union had yet to fall and liberty for eastern Europe was still in the breach. Hayek told us he would debate anyone, anywhere.

While there were debates in the 1970s and 1980s, our sense of that era is that the place where Hayek’s ideas were really resonating was behind the Iron Curtain. There the disputation had to be carried out sotto voce. No doubt lurks in our mind that, broadly put, Hayek’s side — and America’s — won. The western hero of the labor union that cracked communist rule in Poland, Solidarity, was Margaret Thatcher.

The debate today, even with the example of Venezuela, is taking place in America about America’s own economy. Our own instinct is not to take the outcome for granted. Whatever the substantive differences, the rising radicals in the Democratic Party have their share of moxie. All the more apt Mr. Kudlow’s call. Lincoln and Hayek taught how consequential a great debate can be.