Current electoral arrangements and proportional representation
As explained in Chapter 1, the Senate, since present electoral arrangements were introduced in 1948, taking effect from 1949, has been the means of a marked improvement in the representivity of the Parliament. The 1948 electoral settlement for the Senate mitigated the dysfunctions of the single member electorate basis of the House of Representatives by enabling additional, discernible bodies of electoral opinion to be represented in Parliament. The consequence has been that parliamentary government of the Commonwealth is not simply a question of majority rule but one of representation. The Senate, because of the method of composition, is the institution in the Commonwealth which reconciles majority rule, as imperfectly expressed in the House of Representatives, with adequate representation.
Proportional representation applied in each state with the people voting as one electorate has been twice affirmed. In 1977, the people at referendum agreed to an amendment to the Constitution so that in filling a casual vacancy by the parliament of a state (or the state governor as advised by the state executive council), the person chosen will be drawn, where possible, from the party of the senator whose death or resignation has given rise to the vacancy. A senator so chosen completes the term of the senator whose place has been taken and is not required, as was previously the case, to stand for election at the next general election of the House of Representatives or periodical election of the Senate. The previous arrangement had the defect of, on occasions, distorting the representation of a state as expressed in a periodical election. The Constitution thus reinforces a method of electing senators which is itself only embodied in the statute law. The present combination of statute and constitutional law serves to underline and preserve the representative character of the Senate.
If the statute law were amended so as to abandon the principle of state-wide electorates for choosing of senators in favour of Senate electorates, this would not only have the defect of replicating the House of Representatives system, which by itself is an inadequate means of even trying to represent electoral opinion fairly, but would invalidate the special method of filling a casual vacancy now provided for in section 15 of the Constitution. Single member constituencies would probably be unconstitutional, as they would result in only part of the people of a state voting in each periodical Senate election. There are grounds for concluding that anything other than state-wide electorates and proportional representation would be unconstitutional.
The second affirmation of state-wide electorates for the purpose of electing the Senate may be found in the decision of the Commonwealth Parliament, on the basis of a private senator's bill, to remove the authority of the Queensland Parliament to make laws dividing Queensland "into divisions and determining the number of senators to be chosen for each division".
The irresistible conclusion of any analysis of basic arrangements for election of senators is that, for reasons of principle and practice, these features are essential: direct election by the people; equality of representation of the states; distinctive method of election based on proportional representation as embodied in the 1948 electoral settlement for the Senate; elections in which each state votes as one electorate; and filling of casual vacancies according to section 15 of the Constitution.