[Donald Trump ] would make history in so many ways because he is a candidate who eschewed the traditional arts of political campaigns, including field organization, traditional advertising, debate preparation and policy knowledge.

[Donald] Trump has said he will accept the results of the election - if he wins. And he has said the only way he can lose the election is if it's stolen from him. Weeks before any votes were cast, he was predicting widespread voter fraud. So if he loses, what does he do?

Mitt Romney got 59 percent of the white vote in 2012, considered by many to be a high-water mark with this demographic group. Can [Donald] Trump win a higher share of white voters than Romney and get more of them to turn out?

Senate races have tightened along with the presidential race. Watch to see how many Republican Senate candidates outperform Donald Trump - and how many hang on to their seats in states that he loses.

[Donald Trump ] would make history in so many ways because he is a candidate who eschewed the traditional arts of political campaigns, including field organization, traditional advertising, debate preparation and policy knowledge.

The president is under 50 percent approval ratings in all the battleground states. So, you could say that President Obama is defying gravity by still being in a dead heat with Mitt Romney. And one of the reasons that he is, is because the changing face of the electorate are giving him a small boost.

[Hillary] Clinton has also struggled with key groups of voters.