Activists hold a rally to protest the Trans-Pacific Partnership trade agreement in front of the White House on Feb. 3. Trade has become a key issue in the U.S. presidential campaign. Olivier Douliery/Getty Images hide caption toggle caption Olivier Douliery/Getty Images A Nation Engaged Trade Matters In 2016; This May Help You Understand Why April 18, 2016 Candidates vying for president are talking a lot about trade. But trade is not a subject easily summed up in slogans. Here are resources to help you study up on trade and make your own decisions.