After W, everyone thought it can't get worse with the GOP. The same was thought once the Tea Party surfaced. Now we believe Mr. Trump has hit the bottom. We might be proven wrong a couple of years from now. They always find a way to surprise us, but not for the good.
I think though there is a certain point beyond which independents, GOP leaning suburbanites, and some Obama/Trump voters will absolutely not follow. And a significant chunk of the party embracing a conspiracy theory about a deep state stocked with Satan worshiping pedophiles is very much likely to be that point. This is why I believe the embrace of QAnon means permament minority status for the GOP, for as long as that embrace continues.
This sounds familiar. Yeah, I'll believe it when I see it. When one of these pathogens successfully migrates from the media ecosystem to the hive mind, the electoral consequences are typically negligible. Outside of a Republican primary, that is. ~90% of the voters don't know, ~45% of them don't care. And you can win a lot of elections with ~45%. So here's my prediction:
long before the GOP is relegated to perennial minority status, there will be at least one (sympathetic) Congressional inquiry into the claims of QAnon.