Stocks fell by nearly 9 percent on Monday — the worst single-day drop in two decades — after the government’s bailout plan, touted by its supporters as a balm for the current market stress, failed to pass the House of Representatives, setting off a fresh wave of anxious selling.

In yet another day that has shaken the embattled canyons of Wall Street, the Dow Jones industrials fell 777.68 points after it became clear that the legislation could not muster the support it needed to pass the House.