Providing further evidence the postwar rally has run out of steam, even a big merger in biotech couldn't prevent major averages from slumping Monday. As the weakness evident late last week carried over, market internals were the weakest in recent memory, although volume was modest and indices finished off the session's worst levels. After trading as low as 9038.29 shortly after 3 p.m. EDT, the Dow Jones Industrial Average finished down 1.4% to 9072.95. The S&P 500 shed 1.4% to 981.65 after trading as low as 977.40, and the Nasdaq Composite lost 2.1% to 1610.82 vs. its intraday low of 1601.40. In a reversal of recent trends, declining stocks whipped advancers 3 to 1 in both Big Board and over-the-counter trading while new 52-week highs led new lows by a relatively minuscule 60 to 9 and 88 to 9, respectively. Declining volume was 90% of the 1.2 billion shares total on the Big Board and over 80% of the nearly 1.6 billion shares traded over-the-counter. Reflecting the extent of the selling, the one-day Arms Index -- which measures the ratio of advancing issues to declining issues by the ratio of advancing volume to declining volume -- jumped 120% to 2.33. Still, volume was relatively modest, which may provide some solace to the optimists, i.e., evidence that this was just a temporary (and "necessary") setback for an overextended market. Lower volume on down days has been a key characteristic of the rally, particularly since the March lows. "The market had definitely gotten ahead of itself and expectations propelled the market ahead of reality," said Scott Curtis, head of U.S. equity trading at Credit Lyonnais. "The market was due to sell off." Still, market breadth and the overall negative tone of trading suggest something has changed. So dramatically has momentum shifted to the downside that some are discussing likely stopping points for this decline, which actually began last Tuesday for the Dow and on Wednesday for the S&P and Comp. Candidates included the 50- and 200-day moving averages, which began the week at around 8721/8064 for the Dow, 944/891 for the S&P and 1535/1387 for the Comp.