Harold Holt disappeared while swimming at Portsea, Victoria, on 17 December 1967, and was officially presumed dead two days later. The Governor-General, Lord Casey, sent for McEwen and commissioned him as interim Prime Minister, on the understanding that his commission would continue only so long as it took for the Liberals to elect a new leader. 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.