What sort of swing could produce a hung parliament?


On election day I published a blog post looking at how the crossbench had been expanding over time and how that had largely eliminated the risk of a “wrong winner” outcome, where the party losing the two-party-preferred count wins a majority.

I realised the other day that we basically have all the data we need now to revisit this topic and see how things have changed.

The 2022 election saw a massive increase in the size of the crossbench from six (which had been the previous record) to sixteen.

Labor won 77 seats, meaning that a loss of two seats would deprive them of majority and elect a hung parliament. A net gain for the Coalition of seventeen seats would give them a majority. So the “hung parliament zone” is somewhere between those two figures.

When you look at the list of seats that falls within that hung parliament zone, there usually hasn’t been any crossbench seats on that list. After all, you are looking for seats held by a minor party or independent on a slim margin and where the main opposition comes from the major party not in government. There just hasn’t been many seats like that.

That’s different this time around. I wrote previously about the potential paths to power for the Coalition, and quite a lot of the lowest-hanging fruit are in crossbench seats.

The actual range that would produce a hung parliament, assuming a uniform 2CP swing to the Coalition, is 0.4% to 3.5%. This range of 3.1% is actually slightly narrower than the equivalent range in 2019, despite the size of the crossbench growing to almost three times its previous size. There's just a lot more seats the Coalition lost in that narrow range.

William Bowe at Poll Bludger estimates the final national two-party-preferred vote at 51.9%, which is pretty much right in the middle of the hung parliament zone.

If you exclude the crossbench seats (five independent seats and one Greens seat with margins under 3.5%), the hung parliament range balloons out to 0.4-6.5%. So if the newly-elected independents can replicate recent history and solidify their margins, there is a huge range of outcomes that would result in a hung parliament.

So the conclusion at the end of this post, I guess, is that the chances of a hung parliament if there is a small swing to the Coalition are quite high. But if the newer crossbench MPs can increase their margins, it would make it significantly harder for the Coalition to form a majority, and make a hung parliament even more likely.

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  1. Referring to the 2022 election, isn’t the hung parliament range between Labor 2PP 51.5% (0.3% swing to Coalition) to 48.4% (3.5% swing to coalition), putting the election’s 2PP vote of 51.9% outside the hung parliament range, rather than at the middle of it? I found it a bit confusing to have the 2PP margin on the same axis as the hung parliament range, because they are measuring different things.

  2. The red dot is meant to indicate the swing for the national 2PP winner to change, ie. the 50/50 point. So you quote the 51.5%-48.4% range, which is almost perfectly centred on 50%.

    If there was a uniform swing of 1.9%, that would put the result smack-bang in the middle of that range you quote.


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