Wall Street settled lower by late afternoon Thursday as uncertainty over Friday's jobs reports and the presidential election next Tuesday came to a head. 

The S&P 500 was down 0.44%, the Dow Jones Industrial Average slipped 0.16%, and the Nasdaq fell 0.92%. The S&P 500 has now declined for eight consecutive sessions.

Most investors were holding out for the most closely watched economic report, the monthly jobs report, that will be released on Friday. Economists anticipate 173,000 jobs to have been added to nonfarm payrolls in October, accelerating from 156,000 in September. The unemployment rate is expected to dip to 4.9% from 5%, while average hourly earnings are predicted to climb to 0.3% from 0.2%.

Uncertainty over next week's U.S. presidential election kept Wall Street on edge. Stocks have endured a volatile week after a number of polls showed Republican presidential candidate Donald Trump gaining momentum in Electoral College and popular vote polls. A Times/CBS News poll Thursday morning shows Democratic presidential candidate Hillary Clinton holding onto a three-point lead. The poll noted that most voters say their minds have been made up.

Crude oil was also a major weight on sentiment as fears over a global oversupply persisted. Weekly data out from the Energy Information Administration on Wednesday showed a major build in domestic inventories. Stockpiles rose by their most in 34 years, according to the latest data. Meanwhile, skepticism grew over whether major oil producers, including the Organization of Petroleum Exporting Countries, would come to a freeze agreement at a meeting later this month.

West Texas Intermediate crude closed 1.61% lower at $44.61 a barrel on Thursday, its fifth session in decline and its worst close in six weeks.

"Rising OPEC production and last week's sharp build in US crude oil inventories may continue to limit market sentiment," Citi energy futures specialist Tim Evans wrote in a note. "In the near term, we see at least some potential for optimistic statements from OPEC ministers ahead of the November 30 summit to support a moderate recovery in prices, even as we remain skeptical regarding the impact of proposed cuts."

The Nasdaq was the worst performer due to an earnings-driven selloff in Facebook (FB) and Fitbit (FIT) shares. Facebook reported a better-than-expected third quarter on its top- and bottom-lines. The social network earned an adjusted $1.09 a share, 12 cents above estimates. Revenue surged 56% to $7.01 billion, inching past consensus by $90 million. Total daily active users rose 17% to 1.18 billion, while mobile active users surged 22%. Mobile advertising now accounts for 84% of total ad revenue, up from 78% a year earlier.

However, shares fell nearly 6% as growth concerns spooked investors. Facebook warned that advertising growth would "come down meaningfully" once it stops increasing the number of ads in users' news feeds. Facebook has increased ad volume over the past two years to drive revenue growth.

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Fitbit shares crashed 33% after third-quarter sales missed expectations and its fourth-quarter outlook came in short consensus. The fitness wearables company reported a 23% jump in revenue to $503.8 million, but missed estimates of $506.9 million. Fitbit anticipates fourth-quarter eadjusted earnings between 14 cents and 18 cents, well below consensus of 75 cents a share. Full-year earnings guidance was nearly half what analysts had expected.

Services activity in the U.S. weakened in October, according to the latest non-manufacturing ISM index. The measure slipped to 54.8 last month from 57.1 in September, though remained in expansionary territory for its 81st straight month. Analysts expected the index to come in at 56. New orders and business activity both weakened.

Factory orders in the U.S. increased 0.3% in September, up from 0.2% in August. Orders have risen for three straight months. Analysts expected the measure to remain flat at 0.2% growth in September.

Weekly jobless claims rose to a three-month high, according to the Department of Labor. Initial claims for unemployment benefits rose by 7,000 to 265,000 in the past week. The less volatile, four-week average increased by 4,750 to 257,750.

U.S. productivity came in stronger than expected in the third quarter, the Bureau of Labor Statistics said Thursday. Productivity increased 3.1%, better than a 0.2% dip in the second quarter. Analysts anticipated a 2% increase. Unit labor costs rose 0.3%, weaker than an estimated 1.3% increase. Output climbed 3.4%. However, productivity was flat over the past year.

"Smoothing through volatility in the quarterly estimates, the broader picture on productivity growth remains dim," RBS analysts wrote in a note. "We have yet to see any decisive improvement in the trend. Indeed, the bounce in Q3 followed three consecutive quarterly declines, something that hasn't happened since 1979."

The U.K. High Court ruled Thursday that negotiations for the United Kingdom to leave the European Union would not go forth without a parliamentary vote. The decision prevents the government and Prime Minister Theresa May from triggering Article 50, the exit clause that would kick off Brexit.

The Bank of England kept its key policy rates unchanged Thursday and lifted growth forecasts for this year and next. The central bank said that recent data on business activity and sentiment have recovered and that the preliminary estimate of third-quarter economic growth was above estimates. The BoE noted that its next rates decision could go either way.

The Bank also said U.K. GDP would grow 2.2% this year and revised its 2017 estimate to 1.4% from 0.8%. However, it trimmed projections to 2018 and 2019 to 1.5% and 1.6% respectively. 

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