Other than that, South Dakota is a media desert and, because of its poor flight connections, a logistical nightmare from which to campaign for nationwide office.
Obviously convenient flight connections have been the primary consideration in recent GOP VP selection. It explains why Republicans never pick running mates from states like Wyoming and Alaska.
Dick Cheney took a formal residence in Wyoming as a necessity for running for President (he was then living in Texas, and in accordance with the Constitution the President and Vice-President cannot have official (primary) residence in the same State.
Sarah Palin was a catastrophic blunder as a VP choice, and the least of her political weaknesses was being from a politically-small and isolated state -- unless you attribute her gaffes to jet lag. (She makes them without jet lag, so that isn't such a consideration).
Modern campaigns are now done by air, so being near a major air hub (O'Hare International Airport is about as big as there is) is a huge advantage for the President and his staff -- and the efficiency and co-ordination of staff are both essential to an effective campaign. Such may matter less for a VP candidate who doesn't have much control of the logistics of campaigning for anyone but himself. The state now matters less than does proximity to an air hub; Obama could almost as easily have campaigned from Gary, Indiana as from Chicago -- but not from Champaign, Illinois. Gary is a post-industrial dump and Champaign is a nice college town, but one is 30 miles from O'Hare International Airport, and the other is about 150 miles away. Airline connections remain treacherous.