Political advertising refers to the process by which candidates, parties, individuals, and groups promote themselves and their viewpoints through mass communication channels. Political advertising is generally considered a form of paid media in which the promoter (or sponsor) buys the space or time for distributing the advertising message. The paid nature of political advertising is characteristic of the system in the United States; but in many democracies in other parts of the world, candidates and parties are often given free time to promote their messages, at least on the public media channels.