Des Corcoran was 15 when he became a member of the Labor Party in 1941. After leaving school he joined the Army, serving in Korea, Japan, and Malaya, and rising to the rank of Captain. He left the Army in 1961 and was elected to the House of Assembly the following year, playing a role in the Walsh and later Dunstan governments between 1965 and 1968.
With the defeat of the Labor Party in 1968 Corcoran became Deputy Opposition Leader under Dunstan. Labor's victory in the 1970 election saw him become Deputy Premier, taking on a number of ministerial responsibilities including Marine and Harbours and Public Works. He held these portfolios until Premier Dunstan's sudden resignation in early 1979. Corcoran was elected Premier by the ALP caucus soon afterwards.
He also took over the positions of Treasurer and Minister for Ethnic affairs. As Premier, Corcoran displayed a more cautious, less flamboyant style than Dunstan but seemed to gain the confidence of the South Australian public.
So good were the opinion polls in mid-1979 that he decided to call an early election, perhaps to gain a formal mandate for his Premiership. The campaign in the lead-up to the September election, however, was a disastrous one for Corcoran, with business groups and local paper The News firmly siding with Tonkin's Liberal Party. The election, held on the 15th, saw Labor soundly defeated with an 11 per cent swing to the Liberals. He was elected as member for Hartley in the Lower house in 1980.
