I can see this, or if not as utterly bleak, you keep it bittersweet as the book. Johnny Fails, Stillson wins, and someone quietly poisons his drink at his election night victory party. A good question too, do you keep it the early 80s period piece it is now or update the setting?

If you do it present day, it should be about the kid who was at the rally/in the photo and how it’s followed him forever, to the point where he’s gotten every policy internship ever and has great access to new Stilsons, then smash cut to his terrible accident, when the entire thing starts again.

You'd almost have to keep it a period piece. Stillson as written is like ... seventh or eighth tier unhinged in the list of current elected officials. "Institutional mores act as guardrails" is up there with "nobody had cellphones" as far as Useful Horror Stipulations go.