[supplied_demand]

>Most if not all of those declining cities have been consistently run by democrats

And so have most of the growing, thriving cities. Individual cities have very little say in global economic shifts. We are seeing this same story play out in Republican-controlled rural areas.

First some jobs leave (outsource or automation), then laborforce participation declines, next we see drug use increase, which makes more people unemployable, as a result employers leave the area and more jobs are lost. Then you go back to step 1 and re-run.

Trying to cast everything in a partisan light may be blinding you to the similarities.