This is a change of character for the uptrend, suggests that the up move could at least stop for now, at minimum to go into a trading range if not reversing to test the the lower support levels.
Should S&P 500 commits above 2750, this would violate the case and a trading range between 2720–2880 is likely.
Bias - down
Key levels - Resistance: 2780, 2800, Support: 2750, 2717, 2635
Potential setup - look for a test of the of the break down around 2775–2800. A rejection from this level could be a good entry for short. First target at the swing low at 2717, second target at 2635. Stop loss at 2791.