A United States presidential nominating convention is a political convention held every four years in the United States by most of the political parties who will be fielding nominees in the upcoming U.S. presidential election. The formal purpose of such a convention is to select the party's nominee for President, as well as to adopt a statement of party principles and goals known as the platform and adopt the rules for the party's activities, including the presidential nominating process for the next election cycle. Due to changes in election laws, the primary and caucus calendar, and the manner in which political campaigns are run, conventions since the later half of the 20th century have virtually abdicated their original roles, and are today rarely more than ceremonial affairs.