The U.S. stock market Wednesday booked its worst daily decline in months, as concerns about President Donald Trump's FBI controversy weighed on investor sentiment. The Dow Jones Industrial Average shed 1.8% at 20,606, its sharpest decline since Sept. 9, according to FactSet data. The S&P 500 index SPX, -1.82% ended off 1.8% at 2,357, also marking its worst daily drop since Sept. 9. Meanwhile, the technology-laden Nasdaq Composite Index coughed up 2.6% at 6,011, its steepest one-day fall since June 24, the day after U.K. citizens voted to exit from the European Union. The downdraft came on a so-called risk-off day for Wall Street, in which haven assets like the 10-year Treasury note [BX: TMUBMUSD10Y] drew bidders and pushed yields, which move inversely to prices, firmly lower. The 10-year Treasury note was off 10 basis points at 2.22%, and gold futures GCM7, +0.03% another flight-to-safety security, settled sharply higher at $1,258.70 an ounce, representing its highest level in May. Weakness came after the New York Times late Tuesday reported that Trump in February asked the then–director of the Federal Bureau of Investigation, James Comey, to stop his investigation into former national-security adviser Michael Flynn. The report cited a memo from Comey. That has raised questions about the president's ability to pursue the pro-market policies whose prospects for implementation have driven stocks to record levels.