It was expected to be the final measure of Tony Abbott’s increasingly unpopular run as the prime minister of Australia, but he didn’t last the distance. Now, the Canning byelection will be seen as the first test of Malcolm Turnbull’s government.

National eyes will be trained on the West Australian electorate on Saturday morning, as locals go to the polls to decide the replacement for the late Don Randall, whose sudden death in July triggered the byelection.

The two frontrunners are the Liberal candidate, Andrew Hastie, and the Labor candidate, Matt Keogh. Hastie, a 32-year-old former SAS soldier who first met Turnbull and the foreign minister, Julie Bishop, over lunch at a cafe in Tarin Kot, Afghanistan, in 2009, is conservative, devoutly Christian, and has little experience of politics, except for the role he played in advising on Operation Sovereign Borders.

In contrast, Keogh, a 33-year-old commercial litigation lawyer and former commonwealth prosecutor, has worked in politics before, as a policy adviser in the former Labor state government to Alannah MacTiernan, before she resigned from state politics and became the federal MP for Perth. Locally born, as all his signs say, Keogh joined the Labor party at age 16 and is part of its Catholic right.

Both have campaigned on the issues of jobs, infrastructure and tackling rising rates of methamphetamine addiction and, on those issues, there’s not a great deal of difference. Keogh has promised funding for drug rehabilitation services, a cheque he can’t cash unless Labor wins the next general election, and Hastie has promised mandatory sentences for meth dealers who sell to children, a change he has no power over beyond his powers of persuasion with the state government.

Both have also tried to pitch themselves as the natural successor to Randall, who by dint of considerable effort held the swing seat for 14 years. The 62-year-old had a reputation of putting local people above politics, a popular policy with one of the most parochial pockets of the country. Hastie has the same Liberal brand and straight-talk as Randall, but Keogh, a third-generation Kelmscott resident, has the depth of local understanding and knowledge.

A week ago, the race was hard to call. The latest official poll, conducted by Galaxy for the News Corp-owned tabloid the Sunday Times, predicted Hastie would win the two-party-preferred vote 52 to 48.

But that 10% swing toward Labor, away from the comfortable 11.8% margin held by the late Don Randall, was based on phone polling conducted before the change of Liberal leadership and is now a week old. Snap polling conducted since Turnbull was installed as prime minister suggested as much as a 5% bump for the Liberal party in Canning.

A Galaxy poll, released on Friday, had the Coalition ahead on the national two-party-preferred vote – 51 to 49 – for the first time in 16 months.

Dislike of Abbott had decided many an undecided voter before the leadership change. Since Monday night’s party room vote, those same people are inclined to give Turnbull a chance.

Labor’s internal confidence is eroding. Even the bravado of the opposition leader, Bill Shorten, had dimmed on Friday. In his fifth visit of the Canning campaign, Shorten did not say he believed Labor could win the seat – instead, he said Keogh was “doing everything we can to win” and made the simple observation that the outcome of the byelection would not be decided until the polls closed at 6pm on Saturday.

Hastie’s team was more buoyed. On Friday the federal justice minister, Michael Keenan, predicted that Hastie had an “interesting weekend” ahead, while the foreign minister, Julie Bishop, said she “looked forward to welcoming him in Canberra”.

In an unusual twist, postal voters and those who voted early, who are traditionally among the more conservative, could offer some hope to Labor.

As of close of business on Thursday, 10,251 registered Canning voters had voted at prepoll stations, including airport polling booths set up for fly-in fly-out workers to WA’s mining regions. That’s about 9% of the total voter pool of 112,809. Most of those – about 60% – voted before the Liberal leadership spill on Monday night. Another 11,000 or so voters submitted a postal vote.

If that proves cold comfort, a consolation prize for the losing candidate could come in the form of the proposed electorate of Burt, the formation of which has been recommended by the Australian Electoral Commission’s redistribution committee. The new electorate would include the northern tip of the Canning electorate, including the traditional Labor strongholds of Armadale and Kelmscott, as well as parts of the neighbouring Liberal seats of Hasluck and Tangney.

Keogh has already been put forward as the likely winner of the as-yet-unformed seat, a suggestion he brushed aside when asked at a press conference on Friday, saying he was focused on the outcome of the Canning byelection first.

None of the three main party candidates are able to vote in the election – Keogh and Hastie, who both moved into the electorate after being preselected, left it too late to change their enrolments. The Greens candidate, Vanessa Rauland, lives in Fremantle. Of the nine minor party candidates, a handful are eligible to vote, but the rest come from the greater Perth metropolitan area.