New York’s Democratic mayoral nominee, Assemblyman Zohran Mamdani, has proposed a government-run grocery store chain. He says it would pay no rent or taxes — and magically sell food at a lower cost than commercial free enterprise stores.

Forget that this socialist, government-run grocery store would put small, local, largely minority- and legal immigrant-run shops and bodegas out of business. Never mind that it would devastate thousands of New York City’s small grocery owners.

Don’t consider that the math of running a totally government-run socialist grocery store will require a lot of money from hard working taxpayers. It will have to pay for a bureaucracy — and make up for the lost real estate and business tax revenue that would have come from privately owned stores.

Forget centuries of domestic and foreign experiences with big bureaucracies failing to innovate, meet goals, and produce promised results. 

Recreating the Soviet Union’s rationed food lines will hardly improve the lives of the poor in New York City.

If you need proof, look at the most Mamdani-like government-supported grocery store that already exists in America and evaluate the lessons it teaches us.

As Fox News reported, there is a city-owned, government-funded grocery store at Kansas City, Missouri. It’s called KC Sun Fresh, and it is privately managed — but the city owns it, and it is on city property. 

Launching this semi-socialist project was expensive. Instead of private capital from a major grocery store chain, the city has paid tens of millions of dollars taken from the taxpayers to fund the store. 

Like many socialist, big government ideas, KC Sun Fresh started well and then decayed rapidly. 

While the store started with a private sector manager it soon became a community project run by the nonprofit Community Builders of Kansas City. Unfortunately, like many charities trying to compete with private enterprise, the store has rapidly lost ground.

After an encouraging start with 14,000 customers a week, the store has decayed and is now down to about 4,000 customers a week. It is hard to keep fruit, vegetables, and fish fresh with that small a clientele. 

As the nonprofit, government-owned grocery store lost customers, its losses mounted. Last year the taxpayers had to cover an $885,000 deficit. Higher taxes, greater losses, less choice, fewer customers — this is the normal historic pattern of socialist, government-run businesses operating in a free market.

In all fairness, the neighborhood in which KC Sun Fresh operates is a problem. Crime is rampant. There is a remarkable amount of shoplifting, and the threat of crime keeps driving away potential customers.

Mr. Mamdani can argue that Kansas City is different than New York City. He can also argue that a city-funded, charity-run grocery store is not the same as a truly socialist, government-run grocery store chain.

However, if you believe New York City’s government would do a better job than Kansas City’s, you must consider the following questions.

Do you believe the sheer scale and complexity of life and transportation in New York City, population 8.2 million, will make it harder or easier to run a government-owned grocery store than in Kansas City, with 510,000 citizens?

Do you believe the union work rules and union leaders will be easier to negotiate with in New York City than in Kansas City?

Do you believe the New York City bureaucracy — famous for its complexity, slowness, and stubbornness — will be able to meet the daily demand for fresh food and accurate, timely deliveries better than a private owner?

Do you really believe crime, shoplifting, and violence will be better at New York City than at Kansas City?

If New Yorkers convince themselves that Mr. Mamdani’s socialism will magically solve all these challenges, then they deserve a socialist mayor. New York City will shortly thereafter join other failed socialist cities such as Havana, Cuba; Caracas, Venezuela; and Soviet-era Moscow.