its mentioned in the text for the elected category:
These roles are elected by a vote of the players during the day. Players who hold one of these roles do not lose their previous role but gain this one in addition. Players may hold two or more of these positions.
These roles are elected in the particular order of precedence outlined below.
1) Mayor
2) Reporter
3) Guardian
Only one election takes place per day, for the topmost position on this list that is unoccupied at the start of that day. This means that the Mayor is elected first, followed by the Reporter, etc. However, if the Mayor dies, the next day will have a Mayor election instead of whatever role would have been next.
A player that has an elected role may resign (end-night/end-day).