The Parliament of Australia is the legislative branch of the government of Australia. It consists of three elements: the Crown, the Senate and the House of Representatives. The combination of two elected chambers, in which the members of the Senate represent the states and territories while the members of the House represent electoral divisions according to population, is modelled on the United States Congress. Through both chambers, however, there is a fused executive, drawn from the Westminster system.
The upper house, the Senate, consists of 76 members: twelve for each state, and two each for the territories, Northern Territory Islands) and the Australian Capital Territory. Senators are elected using the single transferable vote proportional representation system and as a result, the chamber features a multitude of parties vying for power. The governing party or coalition has not held a majority in the Senate since 1981 and usually needs to negotiate with other parties and Independents to get legislation passed.
The lower house, the House of Representatives, currently consists of 151 members, each elected using full-preference instant-runoff voting from single-member constituencies known as electoral divisions. This tends to lead to the chamber being dominated by two major political groups, the centre-right Coalition and the centre-left Labor Party. The government of the day must achieve the confidence of this House in order to gain and remain in power.