The S&P 500 Index has been choppy throughout 2015. The thing is, it was still edging out new record highs in February, April and May. Finally, since June, we have seen the market reject further advances, and the retreating swings have become stronger and stronger, digging lower and lower.SP500 Daily Chart 8/23(click to enlarge)Last week ended in a sharp drop below a March low around 2040. This swing caused a lot of changes in the technical picture. 1) It completed a rounded top pattern. 2) It put price firmly below the cluster of 200-, 100-, and 50-day simple moving averages (SMAs)3) It dragged the RSI below 30, which shows bearish momentum. Let's say there is a pullback, if the S&P500 has indeed entered a bearish period, we should see resistance by 2080. If price climbs back above 2100, it would have invalidated the current bearish breakout signal. In the short to medium-term, the S&P500 has opened up the 2000 psychological level as well as the lows on the year around 1976, and perhaps the December 2014 low at 1968.