In yesterday’s blog post I analysed the historical evidence for sophomore surge having an impact in Australian federal elections, dating back to 1998.
“Sophomore surge” refers to the phenomenon of a first-term MP performing relatively better than other candidates for their party, doubly so if they defeated a former MP from another party at the previous election.
I found that the evidence is clear, although the effect is not enormous. Other factors remain more important, but the personal vote can create a skew in the pattern of swings.
In the process of calculating sophomore scores for each seat for the 1998-2022 elections, I also did the same for 2025. I have also done this for non-classic seats. They were not part of the previous analysis, but there is strong reason to expect that sophomore surge would be just as much a factor there, if not more so, than in classic seats.
I’ll go through the lists of Labor, Coalition and crossbench marginal seats to look at the pattern of sophomore scores. I’ve also posted a map of every seat in the country showing the score for the incumbent party in each seat.
First up, Labor.
Labor’s sophomore scores aren’t as impressive as might have been the case for past first-term governments in 1998, 2010 and 2016. There’s only a handful of seats that Labor MPs won off contesting Coalition MPs in 2022. Reid and Robertson are the only ones not significantly affected by a redistribution. The feat was also achieved in Tangney and Chisholm but both seats have undergone significant redrawing, adding in new suburbs represented by another Labor MP. Chisholm is quite remarkable, with large parts of Higgins added to the seat.
Labor gained ten seats off the Coalition in 2022. Only six of those seats had incumbent Coalition MPs who contested that election. This includes Higgins, which has been abolished, and Hasluck, which has such a large margin that it doesn’t appear in the table above. But the sophomore surge will be lessened in Bennelong, Boothby, Pearce and Swan, where the Liberal MP had retired.
First-term MPs also replaced retiring Labor MPs Lingiari, Parramatta and Hunter.
Labor also doesn’t have many seats where they are weakened by retirements. Lyons stands out obviously. Also Bullwinkel stands out as a seat where Labor has no sitting MP, and in large parts of the electorate they have lost the personal vote of a previous MP.
Now let’s look at the crossbench marginal seats.
Unlike with Labor’s marginal seats, pretty much all of these seats were won in 2022 off incumbent MPs who contested the election. The only exception was Fowler, where Chris Hayes had retired. This means any sophomore surge is likely to be more concentrated here than in the Labor marginals.
The effect has been weakened in Mackellar, Kooyong, Goldstein and (slightly) Curtin by redistributions, but they’re still pretty strong.
And finally let’s look at the Coalition. They hold 24 seats on margins under 6%.
Of course there are no +2 scores, because the Coalition didn’t gain any seats in 2022. There are a handful of seats where retirements in 2022 mean they may get a relative boost there in 2025 – Casey, Hughes and Flynn stand out. Menzies also has this effect but has been redistributed so significantly that the effect is weakened.
There are also three seats where the sitting Liberal MP is retiring and they stand out as potential weak points: Bradfield, Leichhardt and Forrest. The first two of those seats have definitely grabbed my attention, and perhaps Forrest should too.
Overall sophomore surge effects seem more helpful to the government and especially the crossbench than the Coalition in 2025.
Finally this map shows the incumbency score in each seat. Positive scores are orange, negative scores are grey.