Senator Bernie Sanders’s proposal to give the public an ownership stake in America’s top A.I. companies is quite alarming. He is not simply advocating a sovereign wealth fund that would help the public capture the benefits of A.I.-generated growth. Those funds normally take small stakes in many companies; Mr. Sanders wants the government to take a major stake in industry leaders, giving it both a share of profits and the power to dictate the company’s behavior.

Unlike the normal left-of-center policies Republicans misconstrue as socialism, government ownership of private enterprise is the textbook definition of it. And how do we know it will stop with A.I.? Mr. Sanders’s claim that the government deserves a stake in companies “built on the collective knowledge” could apply to any business that iterates on government-funded research or uses public infrastructure — which is ultimately almost all of them.

The timing of the proposal is particularly perplexing. Donald Trump has already taken direct stakes in some 20 companies, including U.S. Steel and Intel, in return for favorable policy decisions. Do American leftists really want to suggest officially giving his proto-authoritarian regime control of our most influential businesses? It’s a dangerous, half-baked proposal that no liberal should support.