Wall Street suffered from whiplash on Tuesday, as uncertainty over the future of Donald Trump's presidency added to mounting concerns about a pending recession.

The Dow Jones Industrial Average churned through a 350-point swing, closing down 139 points. The S&P 500 fell 0.8 percent, its biggest decline since August; and the Nasdaq Composite Index tumbled by around 1.5 percent, its worst day in a month.

House Speaker Nancy Pelosi, D-Calif., who for months resisted efforts to launch impeach proceedings against President Donald Trump, said Tuesday she will announce a formal inquiry, according to two Democratic sources close to her.

Pelosi's change of heart comes as dozens of House Democrats — now more than two-thirds of the caucus — have come out in support of an impeachment inquiry in the wake of reports that Trump may have withheld aid to Ukraine to pressure officials there to investigate the son of political rival Joe Biden.

Stocks were already trending lower earlier in the day after Trump gave a speech to the United Nations General Assembly, in which he sharply defended his trade policy with China, lambasting Beijing's intellectual property theft and ramping up his accusations that China manipulates its currency.

Markets tumbled again after Pelosi made her announcement, then pared losses when Trump tweeted that he had authorized the release of the "complete, fully declassified and unredacted" transcript of a July phone call he had with Ukrainian President Volodymyr Zelensky that is at the center of the issue.

During President Bill Clinton's impeachment trial in 1998, markets fell prior to the release of independent counsel Kenneth Starr's report on charges of perjury and obstruction of justice related to Clinton's affair with White House intern Monica Lewinsky. However, markets rose as impeachment proceedings continued, hitting an all-time high later that year.

"I think that if I ever got impeached, the market would crash," Trump told Fox News in an interview last August. "Everybody would be very poor."