It's possible that Hillary's nomination process will be so divisive that all of the "new voters" that Obama has pulled in will "stay at home" in greater numbers than the "conservatives" who will "never vote for McCain." Also, will some "Independent" Democrats vote for McCain in protest of a perceived "theft" by Hillary of the nomination? Will they do so in greater numbers than "Ann Coulter" Republicans, who have promised to vote for Hillary over McCain. There will be far more of the former than the latter.
I have to add that many Hillary supporters will vote for McCain, if Obama is the Dem nominee. It's the flip side of the coin, but will make it a closer race, because there are fewer Hillary supporters than Obama supporters to be "disaffected," in the general election.
GOOD LUCK, HILLARY, BARACK, AND JOHN! Anything's possible!