Each state is counted undividually, but each state has a certain number of seats in the house and senate. The bigger the state the more numbers.
If a candidate wins the state they get ALL the seats for that state. For example in California there are 55 seats, so if Obama wins 51% to 49% in California he wins all 55 seats, if he wins 90% to 10% he still wins all 55 seats.
So overall numbers don't really matter, its who wins the biggest and marginal states that count.
