Under the 1964 Constitutional Amendment establishing the Republic of Kenya, the President replaced the Monarch as head of state and the Prime Minister as chief executive. The President was initially elected by the House of Representatives of Kenya, and, after the merger of the House of Representatives and Senate into a unicameral National Assembly, by the National Assembly, for a five-year term. In the event of a vacancy the Vice-President would have served as Acting President for 90 days until new elections were held.