Where there are more than two candidates, the voting system used
for elected mayors is the Supplementary Vote system. Under this
system, voters cast first and second preference votes. After counting
all of the first preference votes, if no candidate has secured
a simple majority of the first preference votes cast, all but
the top two candidates are eliminated. Any of the eliminated candidates'
second preference votes cast for the remaining candidates are
added to those totals, and the one with the most votes is elected
as elected mayor.
Where there are only two validly nominated candidates, the first-past-the-post
system is used.