Under STV, each elector (voter) casts a single vote in a district election that elects multiple winners. Each elector marks their ballot for the most preferred candidate and also marks back-up preferences. A vote goes to the voter's first preference if possible, but if the first preference is eliminated, instead of being thrown away, the vote is transferred to a back-up preference, with the vote being assigned to the voter's second, third, or lower choice if possible (or under some systems being apportioned fractionally to different candidates).