Should Democrats be concerned about maintaining their margins in urban centers?

[Red Wall]

Trump gains were marginal and a product of his improvement with minorities.

But I'd be focused on three black majority swing state cities: Detroit, Philadelphia and Milwaukee. Millwaukee is probably the most problematic one, the post Obama turnout has been lackluster and any dropoff here places a huge burden on Madison to deliver the state to dems. Detroit is losing population but is still the dems biggest vote getter in Michigan and they can't counter its slide even by gaining votes in Oakland and Kent counties. Philadelphia is the least problematic one margins wise given that even under lower % margins Biden netted more votes there than any dem nominee but it has the most R friendly eras especially in South and Northeast Philly. There is also Las Vegas who would be ground zero for a dem hispanic dropoff and a rise in Washoe won't be enough to counter shrinking margins in Clark given 80% of Nevada lives there.