Despite their many differences, Democratic presidential candidate Bernie Sanders and Republican presidential candidate Donald Trump are "delusional" on international trade policy.

So say Will Marshall, president of the liberal Progressive Policy Institute, and Ed Gerwin, a senior fellow there. In an op-ed for The Daily Beast, Marshall and Gerwin criticize Sanders and Trump on trade: "Their proposed fix — shredding international treaties and walling off the U.S. economy — is a textbook formula for economic stagnation… it won't be the 'one percent' who suffer if the populists get their way; it will be U.S. companies with global supply chains and millions of middle-class American workers and consumers."

Marshall and Gerwin criticize Trump's proposed 45 percent tariff on imports from China and 35 percent tariff on imports from Mexico, saying it would hurt American manufacturers, the very people it is supposed to help. China would likely retaliate and raise tariffs against exports from the United States. That would be a huge hit to U.S. manufacturers, since China is our third-closest export partner.

Those tariffs would also be a "giant tax hike" on American consumers.

Both Trump and Sanders mischaracterize free trade in their campaign rhetoric, Marshall and Gerwin say. "Evidently, Trump's vaunted Ivy League education failed to acquaint him with the elementary concept of comparative advantage, by which countries rich and poor can turn trade to their mutual benefit… To Sanders, trade is a conspiracy by Wall Street and corporations to enrich themselves at the expense of working Americans."

Marshall and Gerwin's case for free trade can be summarized in the following quote: "It's true that trade protections would benefit some U.S. manufacturers and workers — including less efficient businesses that can't compete without restrictive rules. But they would harm many others. Studies show that, while tariffs and quotas can promote production and jobs in targeted sectors, they usually do so at an inordinate cost to American consumers and often result in a net loss of jobs in the American economy."

Jason Russell is a commentary writer for the Washington Examiner.