WA Labor leader hopes for Canning swing

Labor's leader in Western Australia, Mark McGowan, says he is hoping for a swing to the party in the Canning by-election, but fell short of expecting a win.

Candidate Matt Keogh told reporters at a Kelmscott polling booth earlier on Saturday that victory is a tough call.

The latest opinion poll points to a 57-43 per cent win for Liberal candidate Andrew Hastie on a two-party preferred basis.

"I'd hope for a swing," Mr McGowan said at a Byford polling booth.

"In ordinary by-elections where the former member passed away, it's 2.5 per cent, so if it's better than 2.5 per cent, I think that would be good."

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.

Mr McGowan said the federal government leadership change had thrown the "whole by-election into flux, into confusion".

"A lot of people will say 'that's a first-time prime minister cut down by his own party colleagues', and I think a lot of people would be unhappy with that," he said.

"But on the other hand, a lot of people didn't like Tony Abbott, so it will have swings and roundabouts for us."