If Donald Trump beats Joe Biden in November, voters can expect four more years of pointless trade conflicts, self-defeating protectionism, inflated costs for domestic companies, and wasted taxpayer dollars.

If Biden beats Trump, voters can expect the same.

There may be genuine policy differences between the two contenders, but when it comes to the bad economics of cynical nationalism, they are singing from the same hymnal.

In 2016, Trump ran for president as an all-out protectionist. From his first hour in office, his hostility to free trade was front and center. “Protection will lead to great prosperity and strength,” he declared in his inaugural address. “We will follow two simple rules: Buy American, and Hire American.”

Last week, Biden issued what amounts to the same declaration. He released an economic plan to “remake American manufacturing and innovation so that the future is made in America by all of America’s workers.” He pledged to “use taxpayer dollars to buy American,” insisting that “when we spend taxpayer money, we should buy American products and support American jobs.” Under his proposal, a Biden administration will pour $700 billion into infrastructure, energy projects, and breakthrough technologies, but federal agencies and contractors will be required to spend the money only on products and research produced in the United States.

The Democrats’ presumptive presidential candidate faults the current administration for not being protectionist enough, and vows to “crack down” in enforcing federal Buy American requirements. Just like Trump — just like generations of protectionists from both major parties — Biden proclaims that permitting taxpayers’ dollars to be spent only on American products made by American companies and American workers will lead to greater prosperity and strength.

That’s exactly what it won’t do.

Protectionism amounts to the claim that society flourishes when it has fewer choices and pays higher prices. In our personal lives, we would never accept this — none of us imagine that our families are better off when our options go down and our costs go up. Yet politicians tell voters again and again that such policies are good for the nation as a whole. They argue that American producers have a right to US tax dollars, and imply that government agencies betray domestic producers when they turn to foreign suppliers for public goods or services.

In reality, it’s the protectionists who betray the public. By depriving taxpayers of the benefit of foreign competition, they compel them to spend more than necessary, or to accept lower quality, on government projects. Protectionism is the equivalent of allowing consumers to shop only at their local grocery or hardware store, barring them from taking advantage of better deals that might be available at the mall or the megastore further away. Granted, that might enrich the local shop owners; it might even enable them to hire a few more employees. But their sweet deal comes at the expense of their customers, who might have gotten more for their money had they been allowed to take their business elsewhere.

Trump accuses Biden of “plagiarizing” his protectionist policies. But “Buy American” mandates didn’t start with Trump. They were part of the stimulus law signed by President Obama in February 2009, for example — with predictably negative consequences. The mandates were causing US companies “a lot of grief,” reported the Wall Street Journal in September of that year. “Buy American guidelines are complicating life for American companies, muddling municipal bidding procedures, and blunting the overall effect of the stimulus.”

Not only do protectionist policies hurt US taxpayers, they frequently hurt US businesses. In the 21st century, supply chains are global, not local. Domestic manufacturers commonly depend on imported parts and raw materials, so that “Buy American” restrictions drive up their costs too. Some vital consumer industries would be crippled without the ability to import what their customers need. Medicine is a good illustration: Many of the generic drugs on which millions of US citizens’ health depends are imported from India and Eastern Europe, where they are manufactured by Swiss and Israeli pharmaceutical firms. Protectionist interference with those supplies would leave Americans not only poorer, but sicker.

For sentimental or patriotic reasons, some Americans may prefer to spend their own money on products manufactured in the United States, even if it means paying more for the privilege. That’s a choice everyone is entitled to. But not with public funds. There is never an economic justification for spending taxpayer dollars on costlier made-in-America products when reliable imports are available at higher quality and lower cost.

“Buy American” mandates are as foolish for America as a “Buy Massachusetts” mandate would be for Massachusetts, or a “Buy Worcester” mandate would be for Worcester. Americans trade across state and local borders because doing so boosts their standard of living and rewards them with an abundance of goods and services. It would be irrational to turn state borders into trade barriers. It’s no less irrational to do so to national borders.

Protectionism may be good politics, but it’s bad for America. If only there were a presidential candidate to say so.

(Jeff Jacoby is a columnist for The Boston Globe).