[x]

"The electors shall meet in their respective states, and vote by ballot for two persons, of whom one at least shall not be an inhabitant of the same state with themselves."

_____

If the two candidates on the ticket are from the same state, either one or the other will have to do without the electoral votes from their state.

[zeestephen]

What happens if one or both of the candidates is not from a state, like Washington D.C. and Puerto Rico?

Also, in the original Constitution, no one voted for vice-president.

Only presidential candidates received votes.

The vice president was automatically the presidential candidate who got the second highest number of electoral votes.