California is 12% of the US economy and 39 million Americans. A president who refuses to engage with the largest state isn't leading the country, he's sulking. Show up and govern.
Go, but make it about policy. California is too big to ignore, and a serious visit on housing, water, crime, and jobs beats another red-meat rally.
A policy-focused visit is the only logical move. Addressing real issues like agriculture and tech benefits the state much more than partisan rallies.
Trump should stay away from California—blue state turf that'd just hand Democrats free ammo and zero upside.