Prime Minister of New Zealand signed a number of international treaties. In 1967, Keith Holyoake became the first New Zealand prime minister to select candidates for the position of governor-general without any involvement of the British government. Holyoake advised the monarch, Queen Elizabeth II, to appoint Sir Arthur Porritt, the first New Zealand–born governor-general. After the mixed-member proportional (MMP) system was introduced in 1996, prime ministers have had to manage minority governments. The skill of MMP management was exemplified by Helen Clark's nine years as prime minister (1999–2008), when her Labour Party remained in power thanks to a range of confidence and supply agreements with
Helen Clark visit she met Queen Elizabeth, Prince Charles and British Prime Minister Tony Blair. Clark's major overseas visit of her third term was a trip to the United States in March 2007, where she met with George W. Bush in Washington. Despite her strained relationship with the President, they agreed on many issues, including working cooperatively in foreign affairs, commerce and the need for both nations to work toward energy security. On 8 February 2008, Clark became the longest-serving leader of the Labour Party in its history (although some uncertainty exists over the exact date when Harry Holland became the first