Political campaigns are orchestrated attempts by political organizations to garner public support through persuasive communication in order to influence public policy in their favor. This broad definition encapsulates all forms of campaigns from those of neighborhood organizations seeking to influence local politicians to the campaigns of political parties and candidates who seek election to office in order to shape policy themselves. In pluralist democracies, campaigns are crucial for representation. Campaigns are a means by which groups of individuals with a common cause can communicate their stance and enable others with similar concerns to join their campaign; thus, campaigns give voice to those individuals and the supporters of their cause. The majority of academic research has focused on the campaigns orchestrated by those seeking election, in particular political parties or candidates seeking to be elected as national president. Due to the levels of resources, the campaigns run by candidates for the U.S. presidency are the most sophisticated and gain most attention. The campaign environment is more complex, however. This entry explores that complex environment, discusses the evolution of political campaigns to their current professionalized form, and concludes with research around campaign effects.