Deputy Prime Minister of Australia 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. Since 1968 only two Deputy Prime Ministers have gone on to become Prime Minister: Paul Keating
Prime Minister of Australia becomes acting Prime Minister in those circumstances. Three Prime Ministers have died in office – Joseph Lyons (1939), John Curtin (1945) and Harold Holt (1967). In each of these cases, the Deputy Prime Minister (an unofficial office at the time) became an interim Prime Minister, pending an election of a new leader of the government party. In none of these cases was the interim Prime Minister successful at the subsequent election. As of , there are seven living former Australian Prime Ministers. The greatest number of living former Prime Ministers at any one time was eight. This has occurred twice: