Wall Street sells off amid weak earnings, election jitters

Illumina shares plummeted 25.6 percent and were among biggest drags on the S&P 500 after the diagnostic test maker's weak quarterly update. Investors have been looking for U.S. corporate earnings to strengthen after four quarters of declines, in order to support relatively high valuations for stocks. Although overall earnings of S&P 500 companies are currently expected to fall 0.7 percent in the third quarter, according to Thomson Reuters data, a typical number of better-than-expected re