Wall Street recorded its sharpest drop in six months Friday as investors, who have been groping for evidence that an economic recovery is gaining steam, responded to renewed signs of weakness calling into question how vigorous the rebound might be.

The stock market was off more than 2 percent after the government reported a significant drop in consumer spending, which has traditionally been the engine of American economic growth. Investors have been looking for consumers to help propel the economy forward once several government programs that have jump-started the economy expire.

Those initiatives, including the popular "Cash for Clunkers" program, were behind the surprisingly strong quarter of growth this summer. After the government reported Thursday that...