A perplexing new chapter is unfolding in Barack Obama's racial saga: Many people insist that "the first black president" is actually not black. Debate over whether to call this son of a white Kansan and a black Kenyan biracial, African-American, mixed-race, half-and-half, multiracial — or, in Obama's own words, a "mutt" — has reached a crescendo since Obama's election shattered assumptions about race. Obama has said, "I identify as African-American — that's how I'm treated and that's how I'm viewed. I'm proud of it." In other words, the world gave Obama no choice but to be black, and he was...