The office of Premier of South Australia was established upon the commencement of
responsible government with the passage of the
Constitution Act 1856. The role was based upon that of the
prime minister of the United Kingdom, with the premier requiring the support of a majority of the members of the lower house to remain head of government. For the early years of responsible government, the office was held in conjunction with that of
Chief Secretary of South Australia, a role that had existed since colonisation, but by the 1890s, this was no longer a convention. No parties or solid groupings would be formed until after the
1890 election, which resulted in frequent changes of the premier of South Australia. If for any reason the incumbent premier lost sufficient support through a successful
motion of no confidence at any time on the
floor of the house, he would tender his resignation to the
governor of South Australia, which would result in another member deemed to have the support of the House of Assembly being sworn in by the governor as the next premier. Informal groupings began and increased government stability occurred from the
1887 election. The
United Labor Party would be formed in 1891, while the
National Defence League would be formed later in the same year. Before the 1890s when there was no formal party system in
South Australia, MPs tended to have historical liberal or conservative beliefs. The liberals dominated government from the
1893 election to
1905 election with the support of the
South Australian United Labor Party, with the conservatives mostly in opposition. Labor took government with the support of eight dissident liberals in 1905 when Labor won the most seats for the first time. The rise of Labor saw non-Labor politics start to merge into various party incarnations. The two
independent conservative parties, the
Australasian National League (formerly the National Defence League) and the
Farmers and Producers Political Union merged with the
Liberal and Democratic Union to become the
Liberal Union in 1910. Labor formed South Australia's first
majority government after winning the
1910 state election, triggering the merger. The 1910 election came two weeks after federal Labor formed Australia's first elected majority government at the
1910 federal election. No "Country" or rural conservative parties emerged as serious long-term forces in
South Australian state politics, the majority folding into the main non-Labor party. ==List of premiers of South Australia==