My friend John Krinsky, Chief Technical Market Analyst from Miller Tabak + Co submits:
We are now seeing the SPX challenge the lower end of the July trading range. The July 26th low of 1676 would be our line in the sand, as a close below that would be a clear change of trend. One other way to view the current rally is by returning to the uptrend line off the November lows. This acted as support many times during this rally, and while price was able to re-claim this trend in July, it is now vulnerable to breaking it once again.
Miller Tabak + Co