Stocks fall again as the Fed signals it could end economic support sooner.

Just as a worrying new variant of the coronavirus has begun to spread, the Federal Reserve chair signaled on Tuesday that the central bank could reduce its support for the economy more quickly, sending a shudder through Wall Street and pushing the S&P 500 negative for November.

A sell-off already in progress accelerated after the chair, Jerome H. Powell, told a Senate committee that inflation was likely to persist well into next year and that the Fed would consider tapering off its purchases of government bonds “perhaps a few months sooner” than...