Polls have opened in Western Australia with Premier Mark McGowan tipped to lead Labor to a victory that could wipe out much of the Liberal opposition.

Voting is underway at more than 700 polling places, with the polls set to close at 6pm on Saturday.

More than 750,000 people have already voted prior to polling day.

With Labor expected to comfortably win a second term, the focus is on how many seats the already-depleted Liberals can manage to save.

A Newspoll published in The Weekend Australian newspaper has Labor leading the Liberals 66 to 34 per cent on a two-party preferred basis.

It would reduce the Liberals to as few as three seats if replicated at the ballot box.

Opposition Leader Zak Kirkup is at risk of becoming the first WA Liberal leader to lose his seat since the 1930s.

The 34-year-old holds the seat of Dawesville by a margin of just 0.8 per cent and has vowed to quit politics if he is voted out.

Such a result would likely spell disaster for other Liberal MPs vying to save their seats.

It would also suggest Mr Kirkup’s decision to concede defeat a fortnight before polling day and warn against giving Labor “total control” was a tactical failure.

Mr Kirkup put on a brave face after voting alongside his father Rob in his electorate on Saturday, saying he had no regrets about the Liberals’ campaign.

“I’m very hopeful of continuing to serve in the district of Dawesville and working alongside as many Liberal colleagues as possible in the WA parliament,” he said.

Asked whether he ever thought it was possible for the Liberals to win the election, Mr Kirkup – who took over the leadership in November – replied “probably not”.

“The reality is, history would be going against us in any case – 1974 was the last time that a first-term government was voted out of office in Western Australia,” he said.

“But what’s at risk right now is that the Labor party is returned with such a landslide majority that there is no one left to hold them to account.”

Mr McGowan visited a polling place in the district of Hillarys, the Liberals’ most marginal seat and one that appears certain to fall to Labor.

The Premier said now was not the time for change.

“National cabinet was formed a year ago today and over that time we’ve dealt with one of the biggest crises the country and world has seen since the Second World War,” he said.

“It’s been an affirmation for me of the great spirit of our state and we want to have the opportunity to make sure Western Australia stays on its current pathway.”

Labor had been expecting Mr Kirkup to survive in Dawesville based on its internal polling.

The party is confident of gaining seats but there is little chance it will gain control of the upper house due to the extra weighting given to regional votes.

-AAP