 McEwen had been encouraged to remain Prime Minister on a more permanent basis but to do so would have required him to defect to the Liberals, an option he had never contemplated.It had long been presumed that McMahon, who was both Treasurer and deputy Liberal leader, would succeed Holt as Liberal leader and hence Prime Minister.However, McEwen sparked a leadership crisis when he announced that he and his Country Party colleagues would not serve under McMahon.