The first is that Malcolm Turnbull will have lost his 30th Newspoll in a row. This is significant, of course, because it was the marker he originally laid down as a reason for challenging Tony Abbott and seizing the prime minister-ship. At the time he insisted "We have to make a change for our country's sake; for the government's sake; for the parties sake." What a difference three years makes.

The second thing we'll learn is that, despite his bumping and bumbling along at his polling nadir, Turnbull will declare that the rule doesn’t apply to him. He’ll insist on continuing as PM.

The final issue is that nobody else has the numbers to challenge. Yet.

Nevertheless, even our egotistical PM is realistic enough to understand his time has run out. Turnbull’s judgement of Abbott back in September 2015 was spot on: there’s absolutely no chance that anyone can overcome such an entrenched deficit. It becomes the story: the prism through which everything the government done is seen.

That's why Turnbull understands he must resign before the election.

Doing this will enable him to pretend he was a success, and this is something that's very important to Malcolm. He will become the first Prime Minister since Robert Menzies to retire, instead of being booted from office by an angry electorate, and it will also allow him to escape the horror of another election campaign.

So what's the timeline?

The issue is coordinating the elections for the Senate and House of Representatives. Although these are normally held at the same time the electoral cycle of both chambers aren't actually in sync.

So while, theoretically, the lower house could continue sitting until early November next year, the only window for a normal election falls between August 4, 2018 and May 18, 2019.

Within that period there are three obvious dates when Turnbull could quite legitimately choose to depart.

The first is September 15, exactly three years after he seized the office from Abbott. However Turnbull never likes to be subject to anyone else's timetable and he’d probably be personally reluctant to resign on this date. The lingering suspicion would always remain that he'd been forced from office, departing under a cloud. He wouldn’t like being so obviously branded a failure.

A far more plausible departure date arrives a month later, on October 24. This is Turnbull's 64th
birthday and he could simply, and quite plausibly, retire on age grounds. It would also allow him to beat Julia Gillard’s record of three years and three days in office, becoming the longest holder of the office since John Howard.

The final date is Australia Day next year. That’s the date Robert Menzies – the only other PM to depart at a time of their own choosing - retired, back in 1966. The problem with this date is that it severely limits any successor's ability to ensconce themselves in the Lodge, before they’d have to rush out and hold an election. That, of course, may not worry Turnbull very much, but it will concern a number of rightfully nervous backbenchers.

A uniform swing of 3.2 per cent (Newspoll’s quarterly average) would see up to 15 coalition members depart, including Peter Dutton, although in reality the government's position may not really be quite that bad. Five of those seats, for example, are in Queensland, the state with the lowest support for the ALP (at just 50.9 per cent), which is probably a reflection of the Labor state government in Brisbane.

The way the uniform swing works, though, is that gains in one place are cancelled by losses in another, and that’s why it’s very difficult to construct a plausible scenario that would see the coalition holding government.

Indeed, some backbenchers fear the reverse: a debacle as people increasingly turn away from the
coalition.

Most of the other vulnerable seats are in NSW and Victoria, both of which are polling particularly poorly for the government. Incumbents tend to lose support at every successive election, and so it’s almost impossible to conceive of a situation where a new PM would be able to turn the tables and coast to victory.

It is, however, the best chance the coalition has of turning around its current dire situation. And if you accept the polls are accurately reflecting the current disenchantment of Australians with their government, there seems little chance that even Turnbull could believe he could turn this round, simply by the sheer force of his personality.

It seems more likely he’ll accept reality and be off, leaving others to fight over the embers of a fading government, headed for inevitable defeat.

Nicholas Stuart is a Canberra writer.