Wall Street stocks dropped for the eighth straight session Thursday on U.S. election uncertainty. Both the S-AND-P 500 and Nasdaq closed lower for the eighth straight day, while the Dow fell for the sixth straight session.

U.S. stocks initially opened higher after fresh opinion polls showed Hillary Clinton having a narrow lead over Donald Trump. But U.S. equities gradually lost earlier gains throughout the day.

Analysts believe the market has not fully priced in the possibility of a Trump win. Others say many investors would prefer to watch this election from the sidelines.

The Vix volatility index, which measures market fear, rose to 22.08, the highest level since the Brexit vote in June. Dow down 0.2 percent at 17,930. S-AND-P 500 slid 0.4 percent at 2,088. Nasdaq lost 0.9 percent at 5,058.