US STOCKS-Wall St sells off amid weak earnings, election jitters
* All 11 S&P sectors in negative territory
* Alcoa, Illumina plummet after disappointing reports
* St. Jude falls after warning on battery flaw in heart device
* Indexes down: Dow 1.2 pct, S&P 1.4 pct, Nasdaq 1.7 pct (Updates to late afternoon)
By Lewis Krauskopf
Oct 11 (Reuters) - Wall Street sold off on Tuesday as disappointing corporate reports gave a sour tone to the start of earnings season and investors digested possible changing dynamics for the upcoming U.S. elections.
Alcoa shares tumbled 10.9 percent after the metals company's quarterly profit missed estimates and lowered its revenue forecast.
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 reports would result in a positive quarter. Continuación...