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. McEwen is reported to have despised McMahon personally. More importantly, McEwen was bitterly opposed to McMahon on political grounds, because McMahon was allied with free trade advocates in the conservative parties and favoured sweeping tariff reforms, a position that was vehemently opposed by McEwen, his Country Party colleagues and their rural constituents.