On 1 and 2 December 1975, a National Congress of People's Representatives voted unanimously to establish the Lao People's Democratic Republic to be governed by the Lao Prople's Revolutionary Party, with prince Souphanouvong as the republic's first president, the position he held until his retirement in 1986. Kaysone Phomvihan became prime minister until 1991 when Khamtay Siphandon succeeded him as prime minister. He moved to be the president in 1998.