Most aspiring presidents and prime ministers face a myriad of challenges as they embark on their journey. Controversial issues, questions about ethics or past conduct, wounds within their party all raise their heads. But the doubts that Barack Obama faces are far more existential than the superficial questions about most candidates. They go to his very core as a person, calling into question his values, his world view, even his patriotism.The disjuncture between who he is and what his background and associations suggest he might be, is so profound that it leads to the most basic of doubts and worries among American voters.Hard racial divisions have softened in America, but fear of the "other" persists. Their possible next president has a strange name. He grew up in Hawaii and Indonesia. He had a Muslim Kenyan father who left when he was a baby. He made his political career in the cesspool of American politics - the traditionally corrupt Chicago Democratic machine. I doubt that this election will be close. Either Mr Obama or John McCain will win it in a landslide, depending on whether or not Mr Obama can fulfil his existential mission of explaining to the American people who he really is.