When election season rolls around there tends to be a lot of discussion around 'swingers' and 'stayers', with a lot more attention placed on the former category of voter.
So what is a swing voter, and why do they matter so much to politicians?
A swing voter is someone who is given to changing their political support from one election to another.
They hold no particular allegiance to any one political party and may vote differently each time.
They differ from the 'stayers' who are the voters who are more likely to vote consistently for one party each election.
It's not to say the swingers are uncommitted voters, though some have described them as being deeply disillusioned with politics in general.
Former Labor Party campaign adviser (and man behind Kevin Rudd's successful 'Kevin 07' ad campaign), Neil Lawrence told ABC Q&A in 2013 that the "swinging voter is often ven disengaged and very hard to get to".
Associate Professor Sally Young from the University of Melbourne believes there may be some truth to that statement.
Her 2011 book How Australia Decides: Election Reporting and the Media argued that those who are more engaged with politics tend to take a firmer stance on parties.
"Much like sports fans, they've picked a side, they have a stake in "the game" and an interest in following it," Professor Young said in 2013.
It's easiest to see how this system plays out in the House of Representatives (or the green ballot paper on election day).
You must number each candidate in order of preference or your vote will be considered informal, and will not be counted.
Number 1 will be your first choice.
"When the votes are tallied, if no candidate obtains more than 50 per cent of first preference votes, then the one with the lowest number of votes is eliminated," said Dr Jacob Deem from Griffith University in Queensland.
"The votes for that candidate are then distributed amongst the remaining candidates according to second preferences.
"If there is still no-one with a majority, the second last candidate is eliminated and their votes are re-distributed as well."
This process continues until one candidate has achieved the 50 per cent simple majority.
"The idea is that preferential voting results in an elected candidate who more closely represents the will of the people," Dr Deem said.
This is why it's important to know who your candidate has chosen to be their second preference choice.
The percentage by which a party wins or loses each electorate is known as the swing.
It determines the popularity of the political parties in that electorate, and it determines whether a seat is 'marginal' or 'safe'.
The Australian Electoral Commission (AEC) defines seats based on how large their swing was in past elections.
A marginal seat will result when the leading candidate receives less than 56 per cent of the vote.
Whereas a safe seat is one where the winning candidate receives more than 60 per cent of the votes.
Marginal seats will tend to receive more attention during an election, but it's important to remember that a safe seat may not always be safe.
In 2016, Liberal seat of Wentworth in Sydney fell out of Coalition control after former Prime Minister Malcolm Turnbull left politics.
Turnbull had held a massive 17.75 per cent margin on the seat and it was considered one of the safest seats in the country.
To put that in perspective, in order for Labor to take the seat they needed to convince nearly 18 per cent of voters in that electorate to change their mind and swing away from the Coalition.
Instead, voters swung nearly 20 per cent away from the Coalition and Independent member Kerryn Phelps ended up claiming the seat.
A similar thing happened with the Division of Warringah on Sydney's Northern Beaches in 2019.
It had been won by former Prime Minister Tony Abbott in 1994. The area had practically been held by a conservative party member since Federation in 1901.
At the least, Warringah had been held without interruption by the Liberals since the seat was created in 1922. It was a stronghold of the Liberal National Party.
Until Independent member Zali Steggall won the seat in 2019.
In order for the major parties to form a government, they need to gain a majority of seats.
Often that means convincing undecided or swing voting populations to rank their party highly on the ballot paper.
In the 2016 election, the Coalition (Liberal Nationals) suffered a -3.0 per cent swing against it, meaning Labor gained a +1.3 per cent swing in its favour.
So after the 2016 election 51 seats - or a third of electorates - were marginal.
Then again in 2019, the Coalition won 77 of 151 seats which was a net increase of one seat from 2016.
At that time, the government managed 51.5 per cent of the two-party preferred system, which is a slim margin.
So when it comes to elections, you're postcode matters. If you live in a marginal seat, you will most likely see more politicians arriving in your city over the next few weeks.
The diplomatic answer to that is: All seats matter, because of course they do. In order for any party to form a majority, all seats and all voters need to matter.
But there are 20 electorates that are particularly prominent in this year's election. And they are:
These are the seats in which the greatest contests are expected, and already in just the first week of the election campaign, we've seen the Prime Minister Scott Morrison and Opposition leader Anthony Albanese hosting events in some of these seats.
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