They have to win all the states in Red, all the states in gold, plus at least 1 in blue to beat Obama, based on the polls.
Frankly if the gap is the same or more (7%+) i think he’ll win all the gold states, plus maybe ND, MT and AZ.
Great page of polling by state:
http://www.realclearpolitics.com/epolls/maps/obama_vs_mccain/#data