Thatcherism describes the conviction politics, economic, social policy, and political style of the British Conservative politician Margaret Thatcher, who was leader of her party from 1975 to 1990. It has also been used to describe the beliefs of the British government while Thatcher was Prime Minister between May 1979 and November 1990, and beyond into the governments of John Major and Tony Blair. An exponent or supporter of Thatcherism is regarded as a Thatcherite.