On his latest speaking tour, the president has continued to talk about a traditional midterm election — in which the country assesses the sitting administration’s agenda — as if it were some epic Manichean struggle, something akin to race relations: Jim Crow, civil rights, and now, most recently, the abolition of slavery. At best, Obama is implying that a referendum on his policies is of similar magnitude to an existential battle like the Civil War; at worst, he implies by analogy that he is the crusading abolitionist and his opponents the forces of slaveholding evil. And all of this from...