US stocks had been comfortably in positive territory prior to news that Federal Bureau of Investigation head James Comey informed lawmakers that he was restarting the probe.
Clinton has been the market’s preferred choice compared with Republican Donald Trump, viewed by many investors as unpredictable. Analysts said the news raises the chances of a Trump win, after weeks during which Clinton handily led the polls.
“One of the things we felt more certain about over the course of the last week or two has been the result at the top of the ballot, and this probably throws that into question,” said Art Hogan, chief market strategist at Wunderlich Securities.
“That’s not going to be good for markets.”
The Dow Jones Industrial Average lost 8.49 points (0.05 per cent) at 18,161.19.
The broad-based S&P 500 declined 6.63 points (0.31 per cent) at 2,126.41, while the tech-rich Nasdaq Composite Index shed 25.87 points (0.50 per cent) to 5,190.10.
The dollar plunged against all the major currencies after the FBI announcement, but regained some territory before the close. The Mexican peso sank against the dollar but also later rebounded slightly.
The Clinton news followed the release of official data showing the US economy grew at a better-than-expected 2.9 per cent pace in the third quarter, data that weighed against Trump, who has repeatedly called the economy “broken”.
Health care stocks were hit hard after drugmakers Amgen and McKesson both highlighted an increasingly cutthroat pharmaceutical pricing environment. Amgen slumped 9.6 per cent and McKesson dived 22.7 per cent.
Other health stocks to fall included Merck, down 4.0 per cent, drugstore chain CVS Health, down 4.4 per cent and pharmacy benefit manager Express Scripts, down 6.0 per cent.
Amazon sank 5.2 per cent after it reported earnings that translated into 52 cents per share, much below the analyst forecast for 78 cents, as a ramp-up in investment caught investors off guard.
Chevron jumped 3.9 per cent after it reported that third-quarter profits fell 36.8 per cent to US$1.3 billion. The results bested analyst expectations and marked a big improvement over the first two quarters of 2016, when it reported losses.
ExxonMobil however fell 2.5 per cent as it reported a 37.5 per cent drop in third-quarter earnings to US$2.7 billion. The oil giant warned it might have to cut its estimate of its commercially viable reserves by nearly 20 per cent due to low oil prices.
Among other companies reporting earnings, Goodyear Tire & Rubber slumped 9.0 per cent, Baidu rose 2.6 per cent and Expedia gained 4.1 per cent. Google parent Alphabet was flat after reporting better-than-expected results.
TROUBLED OPEC TALK HIT OIL
Meanwhile oil prices were hit with a double whammy of the FBI news and uncertainty over OPEC’s ability to negotiate production limits and win the cooperation of non-cartel producers.
The Brent price dropped back below $50 as talks in Vienna failed to work out details of the tentative deal reached last month, although they are expected to continue over the weekend.
“We’ve got some news out of OPEC and things are still very complicating and it sounds like the agreement to come to some sort of freeze or cut is likely not going to happen,” said Oliver Sloup of iiTrader.com.
European markets wobbled ahead of a raft of data and policy decisions in the week ahead.
Frankfurt, London and Paris diverged, while in Asia, Hong Kong and Shanghai ended just down and Tokyo up marginally.
The Bank of Japan and the Reserve Bank of Australia will deliver their latest interest rate calls Tuesday, followed by the US Federal Reserve Wednesday and the Bank of England Thursday.
The eurozone releases third quarter GDP Monday, and the US releases the critical October jobs report Friday.