WI/MI/PA: Which is the most worrisome for Democrats *long-term*?

[Xing]

Of the three states that flipped Republican in 2016 for the first time since the 80s, which should worry Democrats the most in the long-term? I have a feeling that most people here are going to say Wisconsin, but I actually think that the answer is Michigan. It had the strongest R trend of the three in 2016, and that R trend is even more pronounced if you compare it to where it was in 2000. Also, consider that its largest city, Detroit, is bleeding population very rapidly. By contrast, Milwaukee's population seems to have stabilized, and Madison is growing pretty quickly. While Pittsburgh's population is still declining, Philadelphia's has begun to grow again, not to mention it seems as though the Philly suburbs are trending Democratic.

In other words, it seems as though the support Democrats have in the cities of WI/PA may mitigate the collapse they faced in rural WI/PA, but that might not be the case in MI. Also, note that I'm talking long-term here. I'm guessing Michigan will probably flip back in 2020, but in 2024/2028, I wouldn't be surprised if it ended up being more Republican than WI/PA.