Manley was Prime Minister when Jamaica experienced a significant escalation of its political culture of violence. Supporters of his opponent Edward Seaga and the Jamaica Labour Party (JLP) and Manley's People's National Party (PNP) engaged in a bloody struggle which began before the 1976 election and ended when Seaga was installed as Prime Minister in 1980. While the violent political culture was not invented by Seaga or Manley, and had its roots in conflicts between the parties from as early as the beginning of the two-party system in the 1940s, political violence reached unprecedented levels in the 1970s. Indeed, the two elections accompanied by the greatest violence were those (1976 and 1980) in which Seaga was trying to unseat Manley.