The stock market is a leading economic indicator of sorts, because investors tend to buy and sell based on where they believe the economy will be six months or more in the future. Thursday's big drop points to a market increasingly resigned to further economic instability whether or not the bailout plan becomes law. "There are a lot of people who think regardless of a bailout, there's still this economic data and the horror stories out there," said Todd Salamone, director of trading at Schaeffer's Investment Research.

"Certainly, there's a negative psychology."

Investors might get another grim reading about the economy on Friday when the Labor Department releases its September jobs report, one of the most closely watched indicators. The report is expected to show a loss of 100,000 jobs, according to a median estimate from economists. That would be the ninth straight month that the economy has lost jobs.

The Dow fell 348.22, or 3.22 percent, to 10,482.85. The blue chips plunged nearly 778 points Monday, logged a partial rebound Tuesday and finished modestly lower Wednesday; still the Dow has had triple-digit swings every day this week, having fallen more than 200 during Wednesday's trading.

Broader stock indicators also fell sharply Thursday. The Standard & Poor's 500 index fell 46.78, or 4.03 percent, to 1,114.28, and the Nasdaq composite index fell 92.68, or 4.48 percent, to 1,976.72.

Light, sweet crude fell $4.56 to settle at $93.97 a barrel on the New York Mercantile Exchange. Gold and other commodities also declined during the session.

Billionaire investor Warren Buffett said the U.S. has been hit with an "economic Pearl Harbor," and the government must respond quickly. "That sounds melodramatic, but I've never used that phrase before. And this really is one," Buffett said in an appearance on the "The Charlie Rose Show" on PBS stations.

The Labor Department reported Thursday that initial claims for unemployment benefits rose by 1,000 last week to a seasonally adjusted 497,000, above expectations for a 475,000 increase. That's the highest seen since the immediate aftermath of the Sept. 11, 2001, terrorist attacks, and unnerved investors worried about not only about strains in the financial market but also the effect on the broader economy.

Beyond employment, the government reported that orders for manufactured goods fell by 4 percent in August from July. Economists had expected a 2.5 percent decline. It is the biggest drop since a 4.8 percent decline in October 2006.

The dollar was higher against other major currencies, particularly the euro, even after the European Central Bank left interest rates unchanged. Higher interest rates in Europe generally make the euro more attractive to investors than the dollar.

The ECB left its key interest rate unchanged amid concerns over inflation but explored the option of lowering the rate as the financial crisis increasingly affects the continent. The central bank is also weighing a bailout of the region's financial system, similar to what U.S. lawmakers are considering.

That raised the question of whether policymakers globally might be less focused on fighting inflation, and instead trying to come up with short-term solutions to stimulate the economy.

"At some point, you have to face the realities that we have some serious problems and there aren't going to be any quick fixes," said Ryan Larson, head of equity trading at Voyageur Asset Management. "Even if bailouts pass, the fact remains that it might get credit flowing again but won't solve the broader issues out there."