U.S. markets slumped Monday as investors grappled with uncertainty about economic stimulus negotiations and soaring coronavirus cases around the country.

The Dow Jones industrial average fell 650 points, or 2.3%, to 27,686. The S&P 500 index tumbled nearly 1.9% to 3,401, while the tech-heavy Nasdaq composite index dropped 1.6%, to 11,359. The sell-off erased all of the blue-chip index's gains for October.

The United States hit a record high in new coronavirus cases Friday, with more than 83,700 reported, according to data from Johns Hopkins. The resurgence is compounding volatility in the countdown to the presidential election, according to Craig Erlam, an analyst with OANDA.

"Financial markets are getting a reality check, as investors come to terms with the failure of Congress to agree to a pre-election stimulus package and surging covid-19 cases," Erlam wrote in commentary Monday. "Just over a week to go until the U.S. election, it was always likely we could see a little more risk aversion this week given the level of uncertainty."

It's likely to be an eventful week on Wall Street as investors parse central bank decisions from Canada, Japan and Europe, third-quarter gross domestic product data from the U.S. Commerce Department and financial results from the biggest names in tech, including Facebook, Amazon, Apple and Alphabet. (Amazon founder Jeff Bezos owns The Washington Post.)

"The double whammy of a stalled stimulus bill and new highs in cases is a harsh reminder of the many worries that are still out there," said Ryan Detrick, chief market strategist with LPL Financial. "Most of the recent economic data has been strong, but when you see parts of Europe going back to rolling shutdowns, it reminds us this fight is still far from over."

Investors have been closely tracking negotiations over a new round of emergency coronavirus relief, which would pump hundreds of billions of dollars into the U.S. economy. Last week, House Speaker Nancy Pelosi, D-Calif., signaled optimism that prolonged talks with Treasury Secretary Steven Mnuchin would yield progress. Each day's updates on the status of a roughly $2 trillion package coincided with ups and downs in the markets, as investors tried to divine the chances for a deal.

On Friday, however, Mnuchin offered a downbeat assessment of the talks, noting that "significant differences" remain between the two sides. Pelosi had set an earlier, informal deadline to give Congress enough time to pass the legislation before Election Day. But that timetable is now seen as less likely.

"The COVID-19 situation is worrying to investors because they are looking across the pond to Europe, where many countries are increasing stringency measures and implementing a variety of targeted lockdowns, and wondering if that is the future for the US as well," said Kristina Hooper, chief global market strategist at Invesco. "This suggests fiscal stimulus is needed now more than ever, but it looks like it is not forthcoming any time soon. Add to that concerns about a contested election and you have a recipe for market gyrations and sell-offs."

With just eight days to go until the presidential election, former Vice President Joe Biden leads Trump by 9 percentage points nationally, 52% to 43%, according to an average of national polls since Oct. 12.

The market slide also coincides with another covid-19 outbreak at the highest levels of U.S. government, infecting at least five aides or advisers to Vice President Mike Pence, who leads the White House's coronavirus task force.

"Ultimately, until the underlying health care issue truly begins to resolve, we should expect a cloud to continue hang over the global economic outlook and the markets to continue their choppy path," said Nicole Tanenbaum, partner and chief investment strategist, at Chequers Financial Management.

Oil prices sank in response to the rising infections around the globe, which is starting to cause the reinstatement of movement restrictions in some places. Brent crude, the international oil benchmark, fell more than 2% to trade at $40.92 a barrel.

In another reflection of volatility, the yield on the 10-year U.S. Treasury note fell as investors flocked to safer ground. Bond yields fall as prices rise.