Don't be so sure. Why can't he win? I believe he is capable of winning a general election.
There are people who pride themselves on not being "into politics", that haven't voted in years or perhaps never voted before that will come out and vote for a "change" even though they know little or nothing of Obama's record, convictions or ideals.
Don't underestimate the vastness of a shallow Pop culture and Oprah.
Then there are those that will vote for him strictly because of his skin color, in the same way Hillary hoped people would vote for her mainly because of her genitalia.
He will not win the south...hence he will not win the election. Huckabee has a better chance.