Upcoming John Locke Foundation speaker Scott Lincicome writes at the Federalist about free-trade supporters’ approach to Donald Trump.

Donald Trump is on the protectionist warpath, attacking not just America’s trading partners but also its long-held political consensus in favor of open trade. The demise of this consensus is in one sense odd—trade has never been popular with voters, and modest declines in recent polls are typical for election years—but it is no less real: for the first time in decades, both major party presidential nominees are openly skeptical of trade (Trump outright hostile), and congressional leaders are unwilling to consider the Trans-Pacific Partnership (TPP). In a time when our stagnant economy could use a trade-provided boost, such proposals are nowhere to be found.

How did America devolve from the trade advocacy of Kennedy, Reagan, (Bill) Clinton, and Bush to the divisive protectionism of Trump? Some causes are obvious: the Democratic Party, once supportive of trade, has slowly embraced protectionism, its platform and legislative record shifting from trade-friendly in 1996 to mirroring the anti-globalization movement by 2008. Today Democrats, including Hillary Clinton, almost unanimously refuse to support their standard-bearer’s signature trade deal, the TPP.

President Obama also deserves blame: his successful campaigns against the North American Free Trade Agreement (NAFTA) and outsourcing showed other politicians that protectionism can pay political dividends. The president also condoned or implemented discrete trade restrictions like the 2009 safeguard on Chinese tires, while refusing to spend political capital to advocate trade liberalization policies like completed FTAs with Colombia, Panama ,and Korea. …

… But trade proponents in Washington also helped create Trump and the current wave of American trade skepticism. By embracing a mercantilist message to sell trade agreements, one that touts every deal by noting only its ability to generate American exports and trade surpluses, these groups fuel prevalent protectionist myths that imports shrink the economy and cost jobs, and that the trade balance is handy scoreboard for gauging U.S. policy.

At the same time, these “free traders” fail to attack such myths, thus yielding the floor to protectionists like Trump who wrongly blame trade for America’s alleged deindustrialization (though manufacturing output is at record highs) and general economic malaise.