S&P 500 carved out a lower high near 4,540 as compared to the one in July near 4,610 resulting in a deeper pullback. Break below August trough denotes persistence in downward momentum; this is also highlighted by daily MACD which has dipped below equilibrium line.  

The index could drift towards projections of 4,270/4,240, also the lower band of an ascending channel. 

Confluence of graphical levels and the 200-DMA near 4,200 is an important support. In case the index establishes below this, there would be risk of an extended downtrend.