Check out this chart of the S&P 500 with my added notations:First, the 1990 (green) level has been key to the S&P for the past year, either as support or resistance. You will notice that the index is finding support there again today, so far.If 1990 gives way, the next potential support for the S&P would be at its down channel support (red), which currently sits near 1975. A break of both of these levels will, in all likelihood, lead to a test, and possible breach, of the August low.