The largest exchange-traded fund to track Mexico's equity market tumbled on Monday, after Andrés Manuel López Obrador' victory in a presidential election over the weekend added an element of uncertainty into the country's relationship with the U.S. at a time of heightened trade tensions. The victory was seen as moving the country's politics sharply to the left and dealing a major blow to its established political parties. The iShares MSCI Mexico ETF sank 2.5%. The country's stock market has struggled of late, and is down nearly 15% over the past 12 months. The election also weighed on the Mexico peso which fell 1% against the dollar. The Dow Jones Industrial Average fell 0.5% on Monday while the S&P 500 was off 0.4% and the Nasdaq Composite Index was off 0.3%.