While the media and the public tend to focus on the personalities and foibles of the candidates and the horse-race elements of political campaigns, election outcomes often depend as much on the rules that limit candidates' activities and advertising as on the candidates' platforms and personal appeal. How much money may candidates raise? From whom can they accept money? When and how may they spend their campaign funds? What are they allowed to say in their ads?

Informed voters who understand the constraints under which campaigns operate can see past the headlines and the hype...