Election explainer: how are lower house votes counted? And what is 'the swing'?

The alternative vote method, known as preferential voting, is used to elect Australia’s House of Representatives. It was first used at a federal election in 1919 to allow for the anti-Labor votes in rural areas to be split between the Nationalists and the newly emerged Country Party. The first-past-the-post vote system was in use prior to this.

Preferential voting requires electors in single-member electoral districts (”seats”) to numerically order candidates starting with the most preferred (who would get a “1”, or primary vote) through to the least preferred.

At federal elections, voters must cast a preference for all candidates. Failure to do so, or failure to give an ordinal list of preferences, renders the ballot informal. This means it is not counted towards any candidate and is set aside.

How are the votes counted?

When the count for the seat is undertaken, electoral officials begin by counting the primary vote won by each candidate. The successful candidate needs to win 50% plus one vote of the total formal votes cast in the seat. For example, in a seat where 90,000 votes are cast, the winner needs 45,001 votes.

If no candidate has achieved the threshold, the candidate with the lowest primary vote comes out of the count. The eliminated candidate’s ballots are inspected and allocated to the next preferred candidate at full value.

A tally is taken again. If no-one has reached the benchmark, the elimination process continues. The candidate with the smallest total of votes is eliminated; the ballots are inspected and allocated to the next preferred candidate who is still in the count. At all times, the preferences that are allocated retain a full value.

This process continues until a candidate achieves an absolute majority after the allocation of preferences.

The Australian Electoral Commission has done a full allocation of preferences for all seats since 1984. This means election results are expressed in two ways:

• how many primary votes the candidates and their political parties won; and

• the result of the election as a contest between the party that wins a majority of lower house seats and the next best.

This outcome, in turn, will be determined by the result in each seat after the distribution of the preferences cast by those voting for candidates other than those representing the two major parties. This is the so-called “two-party vote”, and is usually expressed as a result comparing the Liberal-National Coalition and Labor.

What is ‘the swing’?

There are 150 lower house seats. The Liberal or National parties comfortably win about one-third of these. Similarly, Labor wins another one-third of these with margins that range from five to 20 or more percentage points.

The final third of the seats, however, have very close margins. These are the seats that the parties fight over, meaning whichever party wins these seats will probably have the lower house majority required to form government.

In each election some voters will change the choice they made in the previous election. They may vote either for the other major party or for a minor party or an independent. The shift in voter alignments between elections is known as “the swing”.

Analysts keep an eye on two types of swing. The first is the primary vote swing. This swing indicates how the voters have responded to the major party in government, and whether the other major party is the beneficiary of shifting alignments. If the other major party is not picking up “swinging” voters, then the shift in support will be going to the minor parties and/or independents.

The “two-party” swing is arguably the more important swing to be observed. This will determine which party wins the close seats. This swing shows the shift of support from the party holding the seat to the candidate who is challenging for the seat after the preferences from voters for all the other unsuccessful candidates in the contest have been allocated.

The ‘how-to-vote’ card

The alternative vote system is quite complicated compared with first-past-the-post voting, for example.

To assist voters in identifying their candidates, political parties publish how-to-vote cards. These leaflets are offered to voters as they arrive at the polling booth and advise those wishing to vote for that particular party on how they should rank their preferences for all the other candidates.

This practice is known in Australian politics as “directing preferences”. However, these leaflets are simply advisory; voters can choose to accept or reject them.

Not everyone requires them, but to a voter who does not know which electorate they are in, does not know the candidates and does not understand how the electoral system works – but wants to cast a valid vote nonetheless – the how-to-vote card is indispensable.

Given these leaflets also advise on the Senate, their usefulness to the uncertain voter is even greater. Scope exists for the parties to try to influence results through the advice they give on preferences.

For major parties, the main purpose of the how-to-vote card is to ensure voters fulfil the requirement of casting a preference for all candidates so that their vote is formal. The preference rankings made by electors voting for minor party candidates, however, may decide which major party candidate will win the seat.

Scope exists for the parties to horse-trade on preferences, provided they are not bound by ideology (it is inconceivable, say, that Family First would direct preferences to the Greens) or rules (the Democrats had a rule never to direct preferences to the major parties).

If wheeling and dealing can be done, it will be undertaken by party secretaries and presidents. This gives the process an opaque, backroom feel to it. It can also seem politically irrational when apparently sworn enemies are shown to have entered into what the party executives will hope is a mutually beneficial arrangement.

Such deals can be the difference between winning and losing seats – and winning and losing executive power.