"More of the same", and "4 more years of Bush" will be the theme this year. McCain has no chance of winning against Obama. Clinton maybe, but not Obama.
Most people don't understand politics to any great depth, but they do know that Obama is a breath of fresh air.
Reagan won by talking about a "new morning in America". Obama is generating a feeling in people that they can once again be proud of America. Something that has slipped away under republican/Bush rule. John McCain will be paired with Bush until we will think that he IS Bush. He won't lose in a landslide, but he will be a victim of a craving for change - simple as that.
Come on now... Obama is not a lock to win against McCain. Let's not get deluded here. McCain is going to be tough to beat no matter how you slice it.