Tony Abbott's prime ministership is again in doubt as Liberals brace for a severe anti-government swing in this Saturday's Canning byelection, potentially kick-starting a fresh attempt to install former leader Malcolm Turnbull in the job.

So fractious is the mood within the government that in one high-risk scenario being discussed, a move to bring things to a head could arise this week given that Parliament is sitting but is not due to sit again until three weeks after the September 19 byelection, making an immediate post-election challenge all but impossible.

However sources in both the pro-Abbott and anti-Abbott camps say a spill this week is unlikely even though a showdown before the end of the year is seen as virtually inevitable.

Fuelling the anxiety is a new Fairfax-Ipsos poll of 1003 respondents taken over the weekend that found voters in Canning are deserting the government in droves, threatening to take its almost 12 per cent winning margin secured in the safe Liberal seat in 2013, down to just 2 per cent after preferences – a swing in the order of 10 per cent.

And with a week to go, the fear is it could get worse.

With Liberals now actively discussing the government's accident-proneness and inability to rise above self-generated distractions, Fairfax Media has been told a new benchmark has been set for the Perth seat, with any swing away of greater than 5 per cent regarded as a fail for Mr Abbott and a trigger for a second attempt at a leadership spill.

The Fairfax-Ipsos survey, which has a maximum margin of error of plus-or-minus 3.1 per cent, found the Liberal Party's supposedly "star" candidate, Andrew Hastie, is likely to retain the seat held by the late Don Randall with 61.8 per cent of the two-party-preferred vote, but with a greatly reduced majority – perhaps only a 52 per cent share to Labor's Matt Keogh on 48.

That is based on second preference flows that occurred at the last election. However, the Liberals' share improves fractionally when respondents stated their second preference, taking the two-party split to 53-47. That is still near enough to translate to a 9 per cent swing.

While Mr Abbott leads Bill Shorten in the strongly Liberal voting area as preferred prime minister, 42-36, both registered negative approval ratings for their respective performances.

The numbers suggest as many as one-in-six people who voted Liberal in 2013 are shaping to support the ALP next weekend.

If replicated across the nation, a swing of 9 per cent would account for some 42 Liberals seats - twice the 21 seats needed by Labor to reach 76 and form government.

One well-placed Liberal source said the government was doing so badly in the so-called "AFL states" of South Australia and Victoria, where the Prime Minister's standing with voters is "toxic", that a switch was now seen as "the low-risk option".

"We're at the point where doing nothing has become the high-risk option and would almost guarantee the loss of vast numbers of seats," said the source.

While Mr Abbott handled the Syrian refugee crisis well last week, the government was again rocked by internal rivalries after a News Corp newspaper story – seen to have derived from the Prime Minister's Office – flagged the removal of half a dozen ministers in a reshuffle.

The Fairfax-Ipsos poll was taken in Canning from September 10-12 just as Perth was consumed with finals fever as both AFL teams played home games.

Pollster David Elliott conceded the finals had made some constituents less willing to participate in the survey when phoned. "We therefore had a much higher than usual refusal rate," he said.

With the tension inside the government now as high as it was in the lead-up to the failed spill motion in February, Mr Abbott struck a defiant tone while campaigning in Perth.

"Well, we're not going to lose the Canning byelection," he said.

"I'm just not going to get into this kind of what would be a good result, what would not ... all I know is that I want the best possible candidate for Canning and that's what we have got in Andrew Hastie."

Two of the hottest issues running in the campaign are the China-Australia free trade agreement, and the claimed epidemic levels of ice – crystal methamphetamine – usage.

Yet around half of all voters in the electorate (49 per cent) indicated they had no view about which party was best placed to manage the ice problem in Canning. Twenty nine per cent nominated Mr Hastie, a former Special Air Services captain, as best positioned to attack the problem, compared to just 12 per cent for Mr Keogh.

More concerning for the government is that a union-funded advertising campaign aimed at raising doubts about the safety of the China-Australia free trade deal is only weakly in positive territory with 43 per cent supporting it and 37 per cent opposed.

- with Matthew Knott

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