Demographics and Politics.

While most of the population is white, Obama has higher numbers than McCain. Obama has 50-52% of the votes while McCain has 44-45% of the votes. A lot of states that would normally vote republican are now voting for Obama. My question is, what brings people to love Obama so much? Is he really just a good speaker or is America wanting a change? Is America sick of having a white president? Are they just sick of the same?
I ask this because Hillary Clinton was a white woman with a lot of experience and a democrat, but she did not get elected. Is America more sexist than racist?
When McCain changed his slogan to "Change" his numbers went up, even though he didn't change any of his ideas.
A question I have about demographics is how do they get all of these numbers? How do they know for sure that all of these numbers are solid? I want to learn more about demographics and I want to learn how to use them and find real averages and numbers.