Beetham joined the then Social Credit Political League, during the 1969 general election campaign, after attending a talk by Don Bethune the Social Credit candidate for Hamilton West. Later, Beetham was elected as one of the vice presidents of the party in 1971. Also in 1971 he ran his first election campaign, an unsuccessfully attempt for a position as a Hamilton City Councillor. His rapid rise in the Social Credit ranks was complete when he was elected Leader in 1972. At 36 he became the youngest leader of a political party in New Zealand's history. He presided over Social Credit's 1972 and 1975 election campaigns, in which they failed to get any members elected.