Stocks accelerated their losses in the final hour of trading to close lower Wednesday, amid ongoing nervousness over the euro zone and after credit-rating agency Egan-Jones downgraded Spain's credit rating to CCC+ from B.
Egan-Jones' latest downgrade for Spain mark's the fourth from the ratings agency since April.
The Dow Jones Industrial Average dropped 77.42 points, or 0.62 percent, to close at 12,496.38 after struggling between small gains and losses for most of the session.
The S&P 500 slipped 9.30 points, or 0.70 percent, to end at 1,314.88. The Nasdaq slid 24.46 points, or 0.86 percent, to finish at 2,818.61.
The CBOE Volatility Index, widely considered the best gauge of fear in the market, jumped to close above 24.
Most key S&P sectors finished lower, led by consumer discretionary and materials. Telecoms squeezed out a small gain.Page 1 of 4 | Next Page