Critics of Shorten, including those within the caucus who support Anthony Albanese, are ready to speak up this weekend if the outcome is grim and they judge it time to rock his leadership.

Albanese, the Labor infrastructure spokesman and a leadership candidate in 2013, has made it clear he will not challenge Shorten. “Absolutely,” he said on Thursday. This will not stop his supporters if Labor does badly.

While some accuse the media of making all this up, the truth is that some Labor MPs have done the numbers and believe Albanese could gain a majority in the federal caucus. They could be completely wrong and they have not factored in the votes from branch members. The point is they are counting.

History is in Shorten’s favour because no government has won a byelection from an opposition in 98 years. With national polls showing Labor has gained ground against the Coalition since the 2016 election, Shorten should be claiming victory on Saturday night. Betting sites have him as the favourite.

If Labor does not lift its primary vote from the 2016 election, everyone will know it has not made enough progress over the past two years to be confident at the general election due by May next year.

Loading

The rise of One Nation makes Longman a special case, with Pauline Hanson on the warpath against Shorten and directing preferences to the Liberal National Party first.

In a worst-case scenario, Labor might get only 30 per cent of the One Nation preferences in Longman, the same result seen at the Queensland state election, compared to 56 per cent in 2016. That could deliver a Coalition victory.

Turnbull does not avoid pressure. The fact that the Liberals have given up on Mayo, the South Australian seat that was once safe Liberal territory, means the Prime Minister has nothing to be comfortable about.

Home Affairs Minister Peter Dutton was frank about his ambitions earlier this week. If the opportunity came up, Dutton told radio station Triple J, he would love to lead the Liberals in a few years.

What if Dutton gets the chance earlier? The polling of individual seats is notoriously unreliable and the national swing against the Coalition could lead to embarrassing losses in Braddon and Longman as well as Mayo. The question may be the scale of the losses.

There is no reason to rule out results on Saturday that put Turnbull’s authority and leadership in question. The fact that he campaigned on Friday while Shorten stayed away may not shield him from the blowback.