Marcia offers to drive Jan around to hang up signs and pass out cookies, but Marcia doesn't get her license until two episodes later. This is the result of the episode "The Driver's Seat" being filmed before this episode but airing later.
Bobby has had braces for the last several episodes except the previous one, yet he has them again in this episode.
When Jan pleads with Peter to be her campaign manager, she says, "Blood is thicker than water", to which Peter replies, "And so is glue." Technically, this is incorrect as Peter and Jan are step-siblings, with separate sets of parents. They are not blood relatives.
When Jan goes back on her promise to babysit her friend Shirley's little brother, Shirley could have dropped off her little brother at the Brady's house. They certainly have enough older responsible people who could have watched him (Greg, Marcia, Carol, Alice).