What is irrefutable is that Wentworth will serve as a bellwether for government prospects under a Scott Morrison-led Liberal Party. In a useful Parliamentary Library analysis of House of Representatives byelections 1901-2017, no byelection has brought about the fall of a government. Loading Replay Replay video Play video Play video However, a number have had consequences far beyond the replacement of a member who has resigned – or been forced out of Parliament.

Labor’s unexpected victory in the north Queensland seat of Dawson in 1966, presaged a Gough Whitlam ascendancy. Conversely, Labor’s loss of Bass in Tasmania in 1975 preceded his demise. Loading If you follow the money in Wentworth, you might conclude betting odds of 1.33 on Liberal candidate Dave Sharma against 3.50 for independent Kerryn Phelps and 7.50 for Labor’s Tim Murray predict a solid Coalition victory.

However, just as racecourse favorites get beaten, those odds seem tighter than justified in a 16-horse race with a plethora of starters from across the political spectrum. This is far more than a post-2000 byelection average of eight candidates. Sharma should win, but this is not a past-the-post certainty in an electorate that is vastly more complicated for the Liberal Party than Malcolm Turnbull’s margin of 17.7 per cent at the 2016 election would suggest. Speaking from Japan, where he now resides, former member for Wentworth Andrew Thomson points out that the seat has a voter churn of about 10 per cent a year, or some one-third over the course of a parliamentary term. This confuses assessments of voter behaviour based on previous election results. Thomson reckons Turnbull’s personal vote would account for about 10 per cent of the Liberal margin. If that “melts away’’ then a conservative cushion becomes “quite thin’’.

Not to be forgotten is that Turnbull, albeit with a vanquished predecessor running as an independent, won in 2004 with a margin of 5.5 per cent. This would be much closer to the Liberal mean in Wentworth these days. The most recent ReachTel poll had Sharma at 40.6 per cent, Labor candidate Murray at 19.5 and Phelps on 16.9 per cent. If Sharma’s primary vote were to slip back into the 30s he would be in big, big trouble, given the near certainty of strong preference flows against him. If there is a piece of electoral history that most closely approximates Wentworth, it is the Wills byelection of 1992 following Bob Hawke’s resignation from Parliament after he lost out to Paul Keating. In that byelection, Labor suffered a massive 19.3 per cent swing against it.

William Bowe, the perceptive Poll Bludger analyst, makes the point that Wentworth remains a difficult electorate to poll compared with a relatively homogenous mortgage-belt division. This is because of the variety of “subcultures’’ there. The electorate includes everything from the super-rich in suburbs like Vaucluse and Bellevue Hill to an apartment-dwelling youth culture in places like Bondi and a solidly middle-class component in the electorate’s southern portion. Along with the once blue-ribbon Liberal seat of Higgins in Victoria this is one of youngest electorates in the country. Added to complications of reading Wentworth is a significant LGBTQI component, many of whom voted for Turnbull because of his support for same-sex marriage. Many of these voters would be likely switch to Phelps, who is gay. Loading

In a state that recorded the lowest percentage "yes" vote for same-sex marriage of 57.8 compared with the national average of 61.6 per cent, Wentworth stood out as a "yes" voting electorate at 80.8 per cent. Only Tanya Plibersek’s electorate of Sydney recorded a bigger "yes" vote in NSW, at 83.7 per cent. Liberal progressives in Wentworth, including a smattering of hedge-fund managers’ wives (a version of the North Shore doctors’ wives), could be excused for believing they are increasingly detached from the party’s right faction on issues like climate, renewables, a coal fetish and attempts to legislate religious freedom. Turnbull’s own ill-starred attempts to accommodate the right on these issues ended up doing him no good at all. Wentworth voters’ verdict on the skulduggery of those who brought him down to shift the party further to the right will weigh. This is no ordinary byelection, and nor are the stakes involved in a betting market that appears, on the face of it, to have mispriced the odds.

Tony Walker is a vice-chancellor’s fellow at La Trobe University and a Fairfax columnist.