Another possibility, rather than the election, is that the Fed is sending Trump a signal to stop his open criticism of Fed interest rate policy.
Trump has criticized the Fed previously, but this time he called the Fed 'crazy'. So maybe the temporary removal of PPT support for the stock market is just a shot across the bow to show Trump who's the boss.
They did that before, back in 2010 with the 'flash crash', which occurred right before Congress was to vote on Ron Paul's 'audit the Fed' bill.