A 32-year-old soldier looks set to be the Liberal Party's candidate for the Canning by-election, after he was recommended by the selection committee.

The member for Canning, Don Randall, died from a heart attack last month, leading to a by-election in his seat, which he held by a margin of almost 12 per cent.

Seven people nominated for Liberal preselection and the selection committee on Saturday night recommended Captain Andrew Hastie be the party's candidate.

The decision still needs to be signed off by the party's State Council.

The ABC understands Captain Hastie had the support of influential Liberals including Finance Minister Mathias Cormann.

Earlier in the day, Senator Cormann was giving nothing away, saying the decision was a matter for the selection committee.

"Let me just say that obviously the circumstances in which this by-election came about are sad and tragic," he said.

"We are looking as a party to select a candidate who, like Don Randall, will fight for the best interests of his or her local constituents and today the Liberal Party preselectors in Mandurah will be making a choice as to who the candidate should be representing us in this election.

"And we will as a Liberal Party do everything we can to win the trust of the people of Canning again to represent them in Canberra."

A date for the by-election has not been announced and Labor is yet to choose its candidate.

The Labor member for Perth, Alannah MacTiernan, said she was confident Labor would get a substantial swing towards it in the by-election.

"I think that the performance of the Abbott Government over the past year has been truly atrocious and people understand that this is not a government that has a vision for the 21st century, so I am very confident that we can get a substantial swing," she said.

"Now, it would be an incredible ask to get to 11 per cent but we're going to be out there trying our best, because we see this as an important election and we certainly see this as a litmus test for the election that will be coming up, we believe possibly in the first half of next year."