CHICAGO — Last month, when hundreds of people showed up at a downtown convention center to hear plans for the Obama Presidential Center (OPC), a campus dedicated to the legacy of Barack Obama, the former president himself arrived unannounced and in full campaign mode to do some hard selling. “This could anchor a transformation of the South Side to create more jobs, more business opportunities, more educational opportunities, more hope. This is our gift. This is us wanting to give back,” he said. But while Obama is embraced in his home town, the OPC has become a flash point for...