Twenty years ago, Dan Savage encouraged progressives to move to blue cities to escape the reactionary politics of red places. And he got his wish. Over the last two decades, rural places have gotten redder and urban areas much bluer.    America’s bluest cities developed their own distinctive culture, politics and governance. They became the leading edge of a cultural transformation that reshaped progressivism, redefined urbanism and remade the Democratic Party. But as blue cities went their own way, as they thrived as economically and culturally vibrant trend-setters, these urban cosmopolitan islands also developed their own distinctive set of problems. Inequality soared, and affordability tanked. And the conversation about those problems stagnated, relegated to the narrowly provincial local section of regional newspapers or local NPR programming. The Blue City Blues podcast aims to pick up where Savage’s Urban Archipelago idea left off, with a national perspective on the present and the future of urban America. We will consider blue cities as a collective whole. What unites them? What troubles them? What defines them?