Randall Forsyth of Barron’s examines the role of trade in the 2016 presidential campaign.

Despite all the parsing about the economic policy prescriptions of the two major presidential candidates, in actuality, the future occupant of the White House won’t be able to do anything about taxes or spending without the approval of Congress. And the House of Representatives seems certain to remain controlled by the GOP, while the Senate could revert to the Democrats. The judiciary is the other branch in the U.S. system of checks and balances that keeps a rein on the executive and legislative branches.

International trade is an exception, points out Brian Horrigan, chief economist at Loomis Sayles. There already is a bipartisan backlash against free trade, with both candidates voicing opposition to the Trans-Pacific Partnership. As for Trump’s promise to “rip up” pacts such as the North American Free Trade Agreement, a president can pretty much do that. And he or she will have wide discretion to raise tariffs, impose quotas, and erect other barriers.

One of the other big weapons on trade is for the U.S. Treasury to declare a country a “currency manipulator,” which Trump has vowed to do in the case of China. Yet, as I wrote first in a cover story that ran almost exactly a year ago (“Trump Is Wrong on China,” Nov. 14), Beijing is no longer manipulating its currency to lower its value; it is doing precisely the opposite. …

… I interrupted the nonstop talk of the presidential race with this admittedly tedious currency discussion to show that the data contradict the claims that China is pushing its currency lower. But more than ever in this campaign season, facts have had a hard time of getting in the way of a good story.

THE EFFECTS OF THE U.S. PRESIDENTIAL race are being directly felt by another currency, the Mexican peso, which has descended a proverbial wall of worry in response to Trump’s rise in the polls. …

… As for the U.S. stock market, the S&P 500 looked as if it might break its losing streak until a slump on Friday afternoon left it lower for the ninth straight session, the longest string of daily declines going back nearly 36 years—longer even than the Cleveland Browns’ slide this year.