 McEwen contended that if Casey commissioned a Liberal as interim Prime Minister, it would give that person an undue advantage in the upcoming ballot for a full-time leader.McEwen retained all of Holt's ministers, and had them sworn in as the McEwen Ministry.Approaching 68, McEwen was the oldest person ever to be appointed Prime Minister of Australia, although not the oldest to serve; Menzies left office one month and six days after his 71st birthday.