Republican Donald Trump’s strong showing in early presidential election results Tuesday sent stock futures tumbling.

Overnight Dow Jones futures plunged more than 500 points shortly after 9 p.m. The Standard & Poor’s index futures was off 58 points and the Nasdaq fell 123 points.

The Mexican peso, which had been surging in recent days on perceptions Democrat Hillary Clinton would prevail, slid as much as 4.6 percent. Trump has been highly critical of the North American Free Trade Agreement, which sent thousands of U.S. jobs to Mexico where labor was cheaper. Trump also has based much of his campaign on berating Mexican immigrants.

Safe havens, including U.S. government bonds, gold and the Japanese yen, rallied, with the benchmark 10-year Treasury note rising as high as 1.89 percent, fractionally higher than Tuesday’s close.

“The fear right now is that Trump could win tonight,’’ Tom di Galoma, managing director of government trading and strategy at broker Seaport Global Securities, told the Wall Street Journal. “We are just seeing a replay of Brexit. Things could get nastier” if Mr. Trump surprised markets by winning the election.

Clinton is seen as a status quo candidate while investors don’t know what to expect from a Trump presidency.

Shortly after 10 p.m. EST, Trump was leading Clinton 48.9 percent to 47 percent with Trump winning 140 electoral votes to 104 for Clinton.

Florida and Virginia were considered tossups and returns from the West Coast had yet to begin flowing. Trump was leading in Michigan, North Carolina, Ohio and New Hampshire.

U.S. markets rallied Monday and Tuesday as polls indicated Clinton was pulling ahead following FBI Director James Comey’s announcement Sunday the investigation into the former secretary of state’s private email server had been closed again without altering July’s decision not to bring any charges.