The issue of whether the Chinese government is putting American steel at an unfair disadvantage has now come up in two consecutive debates. That both candidates have focused on international trade in steel might be surprising, since it is not an issue that directly affects large numbers of voters.

“One of the biggest problems with China is the illegal dumping of steel and aluminum into our markets,” Clinton said Wednesday night. Later, she went after Trump for using Chinese steel in his projects as a real-estate developer. Trump himself had raised the issue in the second presidential debate.

Clinton was referring to a continuing legal dispute between several Asian countries and other nations around the world over subsidies for steel. In June, the U.S. International Trade Commission ruled that Chinese and Japanese subsidies were causing economic injury to the American steel industry. In August, the European Union imposed punishing tariffs on certain types of Chinese and Russian steel in retaliation.

One reason that the candidates are focusing on this rather obscure controversy in international law could be that voters see trade as a political issue, whether or not it affects their own pocketbooks. Researchers who study public opinion on trade have found that Americans are not more likely to oppose international trade if they work in industries or occupations, such as manufacturing, that are vulnerable to competition from overseas.

Instead, Americans’ attitudes on trade are more closely connected with their views on broader questions about American exceptionalism and the country’s position and status in the world. For Clinton and Trump, the issue of Asian steel could be a way to appeal to voters who believe that American power is in decline.