Biden has retreated to South Carolina, where he hopes to hold his support among African-American voters. He seems to imagine himself some sort of living legend among black voters, but he is Barack Obama’s former vice president, not Barack Obama. Biden’s support among black voters is surely transactional and to some large extent a function of his — mostly illusory — strong national polling. Why will African-American voters reach a different conclusion about his suitability than other voters have to this point?