DOUGLAS A. IRWIN is John Sloan Dickey Third Century Professor in the Social Sciences in the Department of Economics at Dartmouth College and the author of Free Trade Under Fire . Follow him on Twitter @D_A_Irwin .
Just because a U.S. presidential candidate bashes free trade on the campaign trail does not mean that he or she cannot embrace it once elected. After all, Barack Obama voted against the Central American Free Trade Agreement as a U.S. senator and disparaged  the North American Free Trade Agreement (NAFTA) as a presidential candidate. In office, however, he came to champion  the Trans-Pacific Partnership (TPP), a giant trade deal with 11 other Pacific Rim countries.
Yet in the current election cycle, the rhetorical attacks on U.S. trade policy have grown so fiery that it is difficult to imagine similar transformations. The Democratic candidate Bernie Sanders has railed against “disastrous ” trade agreements, which he claims have cost jobs and hurt the middle class. The Republican Donald Trump complains that China, Japan, and Mexico are “killing ” the United States on trade thanks to the bad deals struck by “stupid” negotiators. Even Hillary Clinton, the expected Democratic nominee, who favored the TPP as secretary of state, has been forced to join the chorus and now says she opposes  that agreement.
Blaming other countries for the United States’ economic woes is an age-old tradition in American politics; if truth is the first casualty of war, then support for free trade is often an early casualty of an election campaign. But the bipartisan bombardment has been so intense this time, and has been so unopposed, that it raises real questions about the future of U.S. global economic leadership .
The anti-trade rhetoric paints a grossly distorted picture of trade’s role in the U.S. economy. Trade still benefits the United States enormously, and striking back at other countries by imposing new barriers or ripping up existing agreements would be self-destructive. The badmouthing of trade agreements has even jeopardized  the ratification of the TPP in Congress. Backing out of that deal would signal a major U.S. retreat from Asia and mark a historic error.