On 19 December 1967, John McEwen, the long-serving leader of the Country Party in the Coalition government, was sworn in as interim Prime Minister following the sudden death in office of Prime Minister Harold Holt. (There was discussion that deputy Liberal leader and Treasurer William McMahon should assume the office. McMahon had planned a party room meeting on 20 December to elect a new leader, intending to stand for the position himself. However, this was pre-empted by McEwen who publicly declared on the morning of 18 December that he would not serve in a McMahon government.) McEwen was sworn in as prime minister on the understanding that his commission would continue only so long as it took for the Liberals to elect a new leader. Governor-General Lord Casey also accepted the view put to him by McEwen that to commission a Liberal temporarily as Prime Minister would give that person an unfair advantage in the forthcoming party room ballot for the permanent leader. McEwen's appointment was in keeping with the previous occasion when the main non-Labor party was without a leader; Earle Page of the Country Party was interim prime minister between 7 and 26 April 1939—the period between Joseph Lyons' sudden death and the United Australia Party naming Robert Menzies his successor.