4-4.5 has been a level where the $BPSPX:$VIX (BPSPX divided by the VIX) has fallen in a big way in the past. It would be very easy to draw an analogue to the debt downgrade in 2011. There have been threats of a new downgrade and I believe any confirmation of that type would accelerate selling into a sharp point suited for big gains in short-term buying.
I am getting ahead of myself speculating the degree of this potential round of selling. Any word of a positive deal could easily launch the market higher overnight. My sense of the motivations leans toward no deal before the new year and no deal before market declines.
All that being said. If the market is tired of the upside, this relatively subdued selling could in fact be the calm before the storm.