Fundamentally, Obama offered America hope for a new and brighter tomorrow, capturing the imaginations of the populace with a message of real change.
He had the unique ability to transcend race and to bridge the generational divide.
This, combined with Obama's towering intellect, his exceptional oratorical skills, his natural charisma, and his abilities to define his vision for the future in a way the average individual could understand, in a country crying out for new and fresh leadership, made his appeal and his candidacy all but irresistable.
I think Winfield nailed it here, and I'll add they ran the most flawless campaign possible....always always always "staying the course" and staying on message, and lastly they were more successful defining who McCain (true or not) than McCain was.
We have really witnessed brilliance along with history.