You ride into town on the train, then you talk to Rover and all that. Then when you get into town Tortimer comes to you and says, "YOU ARE THE NEW MAYOR. YOU WILL BE MAYOR WHETHER YOU LIKE OR DON'T LIKE IT." Then you will have three choices to answer that.
Any of these three choices
-Okay
-WHAT ARE YOU TALKING ABOUT? YOU CRAZY TURTLE?
-No.
If you say yes. You are automatically made mayor
If you choose the second one. Tortimer explains it to you and you become mayor.
If you say no. Tortimer will yell at you and make you become mayor.
Atleast, that's how I think it should happen.