US main stock indices after previous rally traded lower on Wednesday as investors awaited for the outcome of Greek elections while Moody's and Egan-Jones downgraded Spanish sovereign debt. S&P 500 lost 0.7% or 9.3 points and closed at 1,314.88. Dow Jones Industrial Average fell 0.62% or 77.42 points and finished at 12,496.38. Nasdaq Composite ended 0.86% or 24.46 points down at 2,818.61.