I’m not defending liberalism or their policies. I’m just pointing out that there are other factors for these cities decline. Liberals haven’t helped them and Republicans would not be able to save these places either.
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Pro-business policies, tax incentives for productive residents, removal of government subsidized housing, and a general move away from forced diversity and political correctness toward a meritocracy.
ALL of these things, which USED to be “Republican” values would go a long way to salvaging ANY American cesspool, anywhere.
Additionally, the four examples you gave of liberal-run cities that are doing well, all benefit from tourism and other large net INFLOWS of cash from other areas of, not just the US, but the world at large. Boston, also has a huge and expensive higher education monolith, supported largely on enormous inputs of money from across the globe.
That is a LOT of spare cash for even wasteful, ignorant Leftist bureaucrats to play with.