A new U.S. investigation into Vietnam’s potential currency manipulation and undervaluation could result in a limited amount of tariffs being levied against Vietnamese goods, should U.S. President Donald Trump be reelected in November. On Oct. 2, the Office of the U.S. Trade Representative announced the launch of the investigation under Section 301 of the Trade Act of 1974, which is the United States’ most powerful tool in enacting tariffs on foreign governments with policies deemed harmful to U.S. commercial interests. If concluded by the Trump administration, the investigation -- which will likely take months and could last into 2021 -- would probably find that Vietnam’s currency, the dong, is undervalued due to government policymaking....