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Biggest State Election Landslides

The upcoming Western Australia state election is widely expected to be a landslide for the Labor government, with polls showing Labor upwards of 60% in the two-party-preferred and possibly winning more than 50% of the primary vote. This has resulted in the leader of the opposition Liberals, Zak Kirkup, conceding that his party will not win the election and instead campaigning on the need to return as many opposition members as possible to keep Labor in check.

With WA Labor tipped to win between 60 – 69% of the 2pp vote, it might be interesting to consider how large such a win would be in the historical context. To do so, I’ve looked up state elections in single-winner states (sorry, Tas) and picked three indicators of win size, as follows:

  1. Government 2pp vote: Basically, the share of the 2pp vote the party that formed government won. This has the advantage of directly measuring what share of the voters preferred the government over the opposition, while indicators based off seat share can be affected by malapportionment and other forms of map bias.

    However, in some elections, we may not have a 2pp estimate (e.g. QLD 1974), or the 2pp estimate is affected by issues such as not every electorate having a candidate from either the Labor or Coalition parties. While this shouldn’t have too much effect on our rankings (other than skewing towards recent elections, where calculating a 2pp estimate is more common), I will point out any particular anomalies as we go along.
  2. Government share of all seats: Basically, the % of all seats which returned a government MP. As governments are made and unmade by their seat majorities, this more directly ties into whether or not a government has the numbers to govern.

    As noted above, a government’s % of all seats can be affected by the electoral map they have to run in, which can dampen (if the map has a lot of safe seats) or amplify (if the map has a lot of marginals) a swing, even before factoring historical problems such as malapportionment. There’s also the fact that in some states, the Liberal and Country/National parties did not form a formal Coalition until very recently, meaning the government share of seats is lower than it otherwise would be with a formal Coalition. However, % of all seats helps us capture landslides from eras where we don’t have a 2pp estimate.
  3. Government – opposition seat margin: Basically, the number of government-held seats minus the number of opposition-held seats. This basically functions as a measure of how much wiggle room a newly-elected/re-elected government has in the legislature.

    While govt share of all seats also serves a similar purpose, seat margin better captures how precarious (or, since we’re talking about landslides, safe) a government’s position is. A government with 53% of the seats in South Australia’s 47-member legislature (25 of 47) has a lot less wriggle room than one with 53% of the seats in our federal House of Reps (81 of 151).

The biggest landslides

On each metric:

Newly-formed government’s 2pp share

  1. NSW, 2011 (64.2%)
  2. QLD, 2012 (62.8%)
  3. SA, 1993 (60.9%)
  4. NSW, 1978 (60.7%)
  5. VIC, 1964 (59.0%)
  6. NSW, 1981 (58.7%)
  7. VIC, 1967 (58.4%)
  8. VIC, 1961 (57.9%)
  9. VIC, 2002 (57.8%)
  10. VIC, 1958 (57.8%)

Newly-formed government’s share of all seats

  1. QLD, 2012 (87.6%)
  2. QLD, 1974 (84.1%)*
  3. SA, 1993 (78.7%)
  4. NSW, 2011 (74.2%)
  5. QLD, 2001 (74.2%)*
  6. VIC, 1947 (72.3%)*
  7. VIC, 1977 (72.0%)*
  8. QLD, 2004 (70.8%)*
  9. VIC, 2002 (70.5%)
  10. NSW, 1981 (69.7%)

Newly-formed government’s seat margin over opposition

  1. QLD, 2012 (+71)
  2. QLD, 1974 (+58)*
  3. QLD, 2001 (+51)*
  4. NSW, 2011 (+49)
  5. QLD, 2004 (+43)*
  6. NSW, 1981 (+41)
  7. VIC, 2002 (+38)
  8. QLD, 1977 (+36)*
  9. VIC, 1992 (+34)
  10. QLD, 1980 (+32)*

* : 2pp estimate not available for this election.

One thing to note is that there isn’t a single WA state election in the top ten on any metric – compared to VIC (whose “jewel in the Liberal crown” phase translated into 5 of the top 10 2pp wins), NSW (once widely considered to be a “naturally Labor state”) and QLD (where in 1974 the Labor opposition got cut down into a “cricket team”, and got smashed into a “water polo squad” again in 2012), WA has had very few landslide elections.

Another interesting point of note is that quite a few landslide elections see state Oppositions knocking off unpopular state Governments, running against the backdrop of an unpopular federal Government of the same party as the state Government (NSW 2011, QLD 2012, SA 1993). The exceptions usually have some unique factor (e.g. the Labor split in 50s – 60s Victoria, the malapportionment in pre-1989 Queensland) or are boosted by federal drag (i.e. being of the opposite party to the federal government). While the Labor government in WA won’t have the former factor, it will definitely be boosted by the latter factors (with its successful response to the COVID-19 pandemic standing in for its unique factor).

So how big does Labor need to win to shatter the records? On the 2pp front, it will need 64.3% or more of the 2pp; this seems doable with recent polling estimating Labor at 61 – 68% of the 2pp (at time of writing, our model thinks Labor will win 64.8% of the 2pp on average). With just 59 seats total in its lower house, WA Labor won’t be able to top the third metric no matter how they try, but to set a record for % of all seats won, Labor will need to win 52 or more seats in the Legislative Assembly, which is on the high side (our forecast thinks Labor will win between 45 and 55 seats) but not implausible – our model currently estimates about a 3 in 10 chance that this will happen.

Only time, and the voters of WA, will tell.

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