“The American landscape was once graced with resplendent public swimming pools, some big enough to hold thousands of swimmers at a time,” writes Heather McGhee in her new book, “The Sum of Us: What Racism Costs Everyone and How We Can Prosper Together.” These pools were the pride of their communities, monuments to what public investment could do. But they were, in many places, whites-only. Then came the desegregation orders. The pools would need to be open to everyone. But these communities found a loophole. They could close them for everyone. Drain them. Fill them with concrete. Shutter their parks departments entirely. And so they did. It’s a shocking tale. But it’s too easily dismissed as yet one more story of America’s racist past. McGhee shows otherwise. Drained-pool politics are still with us today and shaping issues of far more consequence than pool access. Drained-pool politics — if “they” can also have it, then no one can — helps explain why America still doesn’t have a truly universal health care system, a child care system, a decent social safety net. McGhee, the former president of the think tank Demos, offers a devastating tour of American public policy, and she shows how drained-pool politics have led to less for everyone, not just their intended targets. I asked McGhee to join me for a discussion about drained-pool politics, the zero-sum stories at the heart of American policymaking, how people define and understand their political interests, and the path forward. This is, in my view, a hopeful book, and a hopeful conversation. There are so many issues where the trade-offs are real, and binding. But in this space, there are vast “solidarity dividends” just waiting for us, if we are willing to stand with, rather than against, each other.