SPX has now lost its 200 DMA support by a meaningful margin.
The up wave from the Feb 2016 low likely either topped in Jan 2018 or Sep/Oct 2018. The current pullback is unlikely part of wave [iv]-down since the Feb 2016 low due to degree violations in price and/or in time. In other words, this is likely a larger degree correction in SPX.
From a longer term perspective, nearly four out of the six surviving EW counts since the 2009 low (4 bullish counts and 2 bearish counts) suggest that further a decline is likely.
Near term, despite the presence of oversold indicators in various time frames, it's prudent to monitor the following most bearish short term scenario ([iii] of 3 down) while be cognizant of various scenarios of a larger potential upswing. Near term dynamic support is around 2558, 2493, 2423, resistance is around 2726, 2821.
Update - 10/29/18
In the short term chart above,
Potential blue [i]-down morphed from a potential contracting DT to a potential expending DT.
Potential red [ii]-up may or may not be finished (expanded flat? with today's drop as its (b)-dn).
For the short term, a parsimonious count for the potential [i]-down shown in the following chart captures the recent price actions well, without degree violations in price (yet).