Hostility toward identity politics—nurtured by Steve Bannon and others—helped propel the rise of Donald Trump. But that feeling is not only to be found on the right. The Columbia professor Mark Lilla, a Democrat and a self-described liberal, says very much the same thing: that vocal opposition to racism, and support for gay and transgender rights, have been costing Democrats election after election all over America. In a controversial new book, “The Once and Future Liberal,” Lilla is highly critical of Black Lives Matter, and goes out of his way to antagonize activists on the left, who, he says, are oblivious to electoral reality. But his position, he tells David Remnick, is in the service of effecting liberal change: “We cannot do anything for these groups we care about if we do not hold power—it is just talk. Our rhetoric in campaigning must be focussed on winning so we can help these people. An election is not about self-expression—it’s a contest.”