Financial markets closed a jittery pre-election week on edge after news that Hillary Clinton’s email troubles had re-emerged. With Donald J. Trump gaining in the polls, investors were preparing for some volatile trading days before and after the election on Tuesday. Traders expect markets to fall sharply if Mr. Trump wins, with Mexican stocks and bonds likely to suffer the most. There are some, though, who think that his low-tax policies and his promise to invest in infrastructure would eventually spur market sentiment. A victory by Mrs. Clinton would lift markets in the short term, but there is little certainty that the rally would last, especially if her victory was a narrow one that increased polarization in Washington. Landon Thomas Jr.