nothing in the constitution says the president and vice president have to be from different states
but
presidential electors can only vote for one person from their state
if both were from a small state like north dakota with only 3 electors it would not matter if the election was won by a large margin
if both were from florida , with 29 or california with 55
you must win by more than that number in the electoral college
this is why when bush and cheney ran together
cheney moved his address to wyoming- to keep the 38 votes from texas in the electoral vote count