I'm doing the "Mayor Elections" quest, and have support of 2/3 guilds (Servants and Mages). However when I go to talk to the leaders of the other two, the only options I have are the regular "Ask some questions" and "Come back later". 

When I select the "Ask some questions" option, the only subdialogue is "That's all."

Any help would be appreciated

You need to get enough reputation for each faction before they give you their election quest.