There's One Born Every Minute.

A nine-year-old Elizabeth Taylor made her film debut in this lively comedy. She plays the spoiled-brat daughter of a pudding manufacturer who has been entered into the town's mayoral race by some of the local businessmen. They have chosen him because they think he is easy to manipulate. As a sales gimmick, the pudding magnate advertises that his product contains the highly nutritious "Vitamin Z." He suddenly begins selling pudding like crazy and soon his political campaign is well-funded. Unfortunately, there is no "Vitamin Z" and when this is discovered, the town fathers try to dump him and show that he is a fake.