I hope nothing untoward happens to Obama--Biden would hardly be an improvement, and if Obama were the victim of violence that could do a lot of harm to the country, more than the Kennedy assassinations or the Rev. Martin Luther King, Jr., assassination. The assassin would be some idiot like Timothy McVeigh or the people who shot Reagan and tried to shoot Ford, but a lot of black people would assume a wider conspiracy.
Anything that goes wrong in the next four years will be blamed on Bush or on white racists--the country would have to be in worse shape than it was in 1980 for anyone to be able to beat Obama. Let's just hope there is a real election in 2016, that Obama hasn't become our Hugo Chavez by then.