Flanked by a dozen American flags, President Obama on Wednesday sought to reclaim the promise that he ran on in 2008: an economy that works for everyone. He called income inequality “the defining challenge of our time,” remembering with evident emotion, “It’s why I ran for president…It drives everything I do in this office.” Yet the divide that began in the late 1970s has only grown under Obama’s stewardship and now threatens to split the Democratic Party as it looks toward a future beyond Obama.