Making Seats "Marginal" At By-Elections Is Meaningless

Last night saw the Labor government get the good end of the stick in the Dunkley by-election, easily retaining a seat that was precariously above the long-term average swing for government vacancy by-elections.  It's no disaster for the Liberals who have got a modest swing with some mitigating factors but they (especially Jane Hume) were out in force last night spinning the outcome as a triumph.  Together with the usual nonsense about first-term governments not in recent decades losing seats and governments not losing by-elections caused by deaths (both based on trivially small sample sizes) I heard a lot about how they had turned Dunkley marginal and they were coming for the seat.

Marginal seat status where a seat is retained is determined by general election results not by-elections (so Dunkley is no more a marginal seat than it was before), but this made me wonder, does getting a seat inside the marginal range at a by-election predict anything at all?  I've found that such seats have historically almost always been retained by the government at the next election, although on average the election-to-election swing has been worse than the national average in such cases.  The idea that the Liberals have put Dunkley in serious danger next time with a swing that is not even bog-average for a government vacancy by-election has no basis.  

Dunkley By-Election Live

DUNKLEY (ALP, Vic 6.27%)

Jodie Belyea (ALP) vs Nathan Conroy (Lib) and others
By-election caused by death of Peta Murphy (ALP)

CALLED 8:42 pm Labor retain

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Updates appear here, scrolling to the top.  When counting is underway refresh every 10-15 mins for new comments.  

Thursday: Labor is now very close to winning the postal count and the 2PP is now 52.71; it is likely to finish between that number and 53.  The Australian published an incorrect article today referring to a 10% drop in turnout; the count does not finish until all postals that can be admitted are received 13 days after polling day.  The turnout is currently 83.5% and there should be about 1% or so to come; the turnout decline will be smaller than at least 16 of the last 20 by-elections, potentially 18.  Media should not publish turnout doomery articles without consulting with the AEC or someone who has a clue.  

Tuesday: With vote totals unlikely to change by even 1% from here it's worth noting an outstanding performance by the uComms seat poll.  I've been critical of poor results from this pollster recently (especially Tasmania 2021) but this one is remarkably good by seat poll standards especially. uComms' numbers with undecided redistributed are below with the actual current numbers in brackets:

ALP 40.1 (41.1)

Lib 39.3 (39.3)

Grn 8.2 (6.3)

LTN 1.6 (2.5)

Ind/Other 10.8 (10.8)

2PP 52 (52.6)

n=626.

2024 Dunkley By-Election

DUNKLEY (VIC, ALP, 6.27%)  By-election March 2
Jodie Belyea (ALP) vs Nathan Conroy (Lib) and others
Cause of by-election: Death of previous incumbent Peta Murphy
Outlook: interesting; seat margin is just above average swing for government vacancies

Early this year we'll get the first electoral test for the Albanese Government on its own turf when the division of Dunkley goes to the polls in sad circumstances after the death of popular previous MP Peta Murphy.  Last year Labor sensationally captured Aston from the Liberals during a period of honeymoon polling, while the Coalition had a pretty good swing result when it retained the uncompetitive seat of Fadden in Peter Dutton's home state.  By-elections are more random and a lot less predictive than politics junkies tend to think they are, but an outer-suburban seat, on a loseable margin, with the honeymoon gone, seems much more significant.  

The by-election has been announced for March 2.  The writ will be issued Jan 29 with close of nominations Feb 8.

2016 House of Reps Postcount: Vanilla Reps Seats

Expected final outcome Coalition 76 Labor 68 Others 5 Undecided 1

Herbert: Labor leading, much too close to call, recount very likely (moved to new thread)

Coalition assumed to win: Grey, Dunkley, Chisholm, Gilmore, Flynn, Forde, Capricornia
Labor assumed to win: Batman, Cowan, Hindmarsh, Melbourne Ports (see separate thread)

Note: You can now vote in the sidebar Not-A-Poll on what will be the closest seat!

Introduction

This thread deals with the standard (hence the "vanilla" in title) two-party preferred seats at the 2016 federal election, as distinct from more exotic offerings like Grey and Melbourne Ports which have their own threads.  Usually the Coalition performs slightly better on post-counting than Labor and for this reason I have (for now) not included Robertson, Petrie, Dickson or La Trobe, in all of which the Coalition leads by more than 1000 votes.  Should any of these close up I may cover them. In 2010 and 2013 Labor never won any seat in which the Coalition had more than 50.53% at the end of the ordinary votes.  However with the different mix of postal votes (see below) perhaps Labor might make such a gain somewhere.