The basic premise was that the president of the US was using the fear of an underground communist terrorist group to move the country in an ever-more totalitarian direction.
At the beginning of the movie the characters believe that the president just made up the communist group for his own nefarious purposes. But toward the end of the movie they start believing that the communist group is real, and that the president is its leader.
I couldn't help thinking of our current situation.
I started “believing that the communist group is real, and that the president is its leader” long before the POS was elected..
PKD has a bunch of great stories.