Malcolm Turnbull should head to bed knowing whether voters in Canning back his party but it will likely be a restless night for his ministers.

The prime minister is set to reveal his new front bench on Sunday with Social Services minister Scott Morrison widely anticipated to be named treasurer in place of Joe Hockey.

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Reports also suggest Education Minister Christopher Pyne, who backed Mr Turnbull in the ballot, will move to defence.

Employment Minister Eric Abetz and Defence Minister Kevin Andrews are expected to be dumped from cabinet, and Michaelia Cash, Marise Payne, Kelly O’Dwyer, Arthur Sinodinos and Simon Birmingham are considered likely for promotion.

The new ministry will be sworn in on Monday but Mr Turnbull remained tight-lipped about the reshuffle when questioned on Saturday.

Meanwhile, the result of the by-election in the federal Perth seat of Canning were expected to be known on Saturday night.

Labor appears to be bracing itself for a loss but Liberal candidate Andrew Hastie said during the afternoon he wasn’t taking anything for granted and planned to campaign until the last minute.

The latest opinion poll has pointed to a comfortable win for Mr Hastie at 57-43 against Labor candidate Matt Keogh on a two-party preferred basis.

When questioned before polls closed Mr Keogh said he was “definitely hopeful” although he conceded it was a tough ask.

While Mr Keogh was flanked by his family and the Labor faithful, in nearby Byford Mr Hastie was surrounded by a sea of supporters and family as well as Julie Bishop.

The foreign minister defended the absence of Mr Turnbull on the campaign trail on Saturday, saying he was too busy to visit Perth in support of Mr Hastie.

“Malcolm would have been here if we’d asked him to,” she said.

The by-election was previously considered a referendum on former prime minister Tony Abbott’s leadership but is now being touted as a measure of Mr Turnbull’s appeal in the nation’s top job.

The by-election was triggered by the sudden death of sitting Liberal MP Don Randall, who won by a 12 per cent margin in the 2013 federal poll.

– AAP