The Australian Senate has 76 members. The six states return twelve senators each, and the two mainland territories return two senators each, elected through the single transferable voting system. Senators are elected for flexible terms not exceeding six years, with half of the senators contesting at each federal election. The Senate is afforded substantial powers by the Australian Constitution, significantly greater than those of Westminster upper houses such as those of the United Kingdom and Canada, and has the power to block legislation originating in the House as well as supply or monetary bills. As such, the Senate has the power to bring down the government, as occurred during the 1975 Australian constitutional crisis.