With Clinton and then later on with Obama (JE, too, unfortunately) people were passionate about each. They believed in their candidacy.
That is not the case. We have gone on a continual swing from one Non Romney to the next. Each Non Romney giving just as much as the public can take of their ineptitude before swinging to the next Non Romney.
The only passion people have is their hatred of Obama. There is no real belief in any candidate. The polls keep swinging from one to the next, and Santorum is just the only guy left after Gingrich's scumbag credentials have been highlighted, and conservative media heads like Limbaugh and Coulter have absolutely trashed him as uncredible.