Shutting down the primaries makes little sense. Another talking point for the left- “See! They want a dictatorship!”
It protects the GOP from the unmitigated disaster that would unfold if states like California are successful in keeping Trump off the primary ballot over his refusal to release his tax returns.
What would happen if we get to the spring of 2020 and Trump isn't even eligible to appear on a primary ballot in a bunch of heavily Democratic states that comprise 40% or more of the Republican Party delegates?