By ABC's Barrie Cassidy Friday 4 September 2015

Photo: Never before has a single electorate held the fate of a serving prime minister in its hands. (ABC News: Andrew O'Connor)

Never has a by-election been framed so unambiguously around a prime minister - lose Canning and you're gone. It will be a nervous time and there is no precedent for this, writes Barrie Cassidy.

Forget all this talk of precedents around the critical Canning by-election in Western Australia. There are none.

Never before has a single electorate held the fate of a serving prime minister in its hands.

By-elections like Bass in Tasmania have spelled the beginning of the end of governments; and Aston in Victoria marked the turning point for a government previously in trouble.

But neither, and none before or since, have been framed so unambiguously around the prime minister. Lose and you're gone. And that is not just accepted wisdom among most commentators; it's agreed unofficially and spoken of privately by some senior Liberals who supported Tony Abbott in the February leadership spill.

And those same people are laying down markers along the way. A swing limited to about 8 per cent would be seen as a relief. Double figures would indicate a very tough federal election and might even lead to a December party room showdown. And a loss (11.8 per cent) or worse, would be disastrous. Some of those who stuck with Abbott in February on the basis that he deserved more time had this period in mind for a review.

They argued privately at the time that the Prime Minister and the Treasurer should be allowed to bring down another budget, and then a few months would need to go by before its impact, both politically and economically, could be judged.

Abbott though has hit two major hurdles in the polls this year - Prince Phillip and Bronwyn Bishop. The controversy around those two individuals caused the Government to slide beyond the typical four-point deficit. Abbott eventually recovered from the knighthood debacle to settle back around 48 per cent two-party preferred.

But he hasn't yet been able to do that since "chopper gate". And that's because the troubles keep on coming. First the Dyson Heydon issue, then the bungled Border Force operation, and all the while constant and ill-disciplined chatter. Comments by Immigration Minister Peter Dutton this week served to underline the depth of the internal problems. If Abbott cannot regain some of that lost ground in national polls before Canning, and that seat falls to Labor, judgments will be harsh and swift.

It will be a nervous time. The Coalition has a good candidate going for it, but not much else.

At the last election, Labor, after a tumultuous time in office, was on the nose, and nowhere more so than in Western Australia.

The mood was dark, even though the economy was still booming and the steam hadn't yet gone out of state projects.

Now the economy has stalled and governments - not political parties - are feeling the pressure. The previously popular state government led by Colin Barnett, for example, is now - according to Newspoll - trailing Labor after having won the last election with 57 per cent of the two party vote.

The late Don Randall with his anti-Canberra pitch was a popular local member, so popular that Labor virtually ran dead at the last election.

Add all that to the average federal by-election swing of 5-6 per cent and you can see why the polls suggest it will be close.

Of course it's a test for Bill Shorten as well. He will need to do much better than the average to avoid criticism.

But it's not his job on the line. And it's not Joe Hockey's either. Not on his own. The spin out of Coalition ranks this week suggested that in the event of a loss, it might save Abbott if he throws Hockey overboard. The stronger view seems to be that the fate of the two is tied together.

Depending on the result, the Canning by-election might signal the beginning of a comeback for Abbott and his Government - just as Aston did for John Howard. It might mean the end of his leadership. Or it might mean nothing at all. The figures on the night will determine that. And this time if a leader falls it won't be in the dead of night leaving an electorate stunned. It will have a basis in fact, the result of a real poll.

And no precedent.

Barrie Cassidy is the presenter of the ABC program Insiders. He writes a weekly column for The Drum.

Abbott's future to be decided in Canning - The Drum (Australian Broadcasting Corporation)