Water. That, more than a (possible) return of the former guy* is what's going to change this country. Climate change is accelerating at a faster pace than most predicted. People who moved to California, Texas, Arizona, Florida, will move back to places like Detroit, Cleveland, Hartford, Buffalo Chicago and Milwaukee. Developers will rebuild in these cities, after abandoning them 60 years ago. Vegas is losing population (20 years ago. everyone had lawns, now, not so much). California lost population for the first time in history in the Census. Any state west of the Rockies will become uninhabitable in the next 15 years.