Each of the six states is represented in the Senate by twelve senators, and each territory by two. Elections in the Senate are carried by party lists. Senators are elected for the term of six years. Every three years, half of the Senate is reelected. Senators from the territories are elected for half of the usual term, i.e. for three years.
Senators are elected for a fixed term, commencing on 1 July following the election, and ceasing on 30 June six years later. Normally, senators are elected at the same time as members of the House of Representatives, but because the newly-elected Senators may take their places only on July 01, the new Parliament will for some time comprise a new House of Representatives and a substantially old, lame-duck Senate.
The Constitution allows to change the number of senators; however, each original state must preserve balance of representation and have at least six senators per state. This provision does not concern newly-joined states and territories. In accordance with the Act of Parliament of 1973, the Australian Capital Territory and the Northern Territory elect two Senators each.
The Commonwealth of Australia Constitution Act (Imp.) of 1900 established the Senate as part of the new system of dominion government in newly-federated Australia. From a comparative governmental perspective, the Australian Senate exhibits distinctive characteristics. Unlike upper houses in other Westminster system governments, the Senate is not a vestigial body with limited legislative power. Rather it was intended to play, and does play, an active role in legislation. The Australian Senate was in part modeled after the United States Senate. This structure was proposed in order to give less populous agricultural states added voice in a Federal legislature.
According to the Constitution, the Prime Minister serves as a member of the lower house, the House of Representatives, but ministers of his cabinet may come from either house, and the two houses have almost equal legislative power. In particular, it is caused by the desire of the underpopulated agricultural states to have a chance to protect their own interests, like deputies in the House of Representatives can do.
The Australian Senate, like many other upper houses of parliaments, is intended to provide equal representation to all regions, and, due to this fact, e.g., Tasmania, with a population of 450,000, elects the same number of senators as New South Wales, which has a population of 6 million. Nevertheless, the proportional election system within each state ensures that the Senate incorporates more political diversity than the House of Representatives, which is basically a two party body. The elected membership of the Senate more closely reflects the voting preference of the electorate in terms of residence, age and interests, and that is why this body is less politicized in its approach to legislation.