Stocks were mixed near midday Monday after a key manufacturing gauge stumbled into contraction territory. Earlier Monday, the Institute for Supply Management's November manufacturing index slipped to 49.5, indicating that factory activity contracted for the month. The reading was also the weakest in early three years. The Dow Jones industrial average fell 0.2% and the S&P 500 slipped a fraction. Both were up as much as 0.5% at their session highs.