Premier Roger Cook was buoyed by two poll results on Friday that pointed to his party's victory as he delivered his final pitch to voters.
But he said the only poll that mattered was Saturday's and the election result.
"We're not taking anything for granted," he said, adding Labor's candidates would campaign until the polls closed at 6pm.
"We are staying humble."
Labor holds 53 of 59 seats in the WA lower house, after its unprecedented landslide victory in 2021, under then-premier Mark McGowan.
This was mainly because of the party's handling of the COVID-19 pandemic and its closed border policy.
The Liberals and Nationals, which have three seats each, would need a swing of more than 20 per cent to form a coalition government.
Mr Cook is facing his first election as premier after Mr McGowan stood down in 2023.
The surveys predict a comfortable win for Labor, with about 57-43 per cent of the two-party preferred vote, although a predicted 12-13 per cent swing could put up to 11 seats in reach of the Liberal Party.
That's not on the cards but the Liberals are expected to regain a number of previously safe Perth seats in the inner-city and western suburbs, including Nedlands and Churchlands, where high-profile Perth media personality and the city's Lord Mayor Basil Zempilas is the party's candidate.
Cost of living and housing are the main issues for WA voters.
Health, education, regional services, state infrastructure and crime have also been targeted by the parties during the campaign.
Liberal leader Libby Mettam said Labor had taken voters for granted after eight years in government and it was time for a change.
"If Labor are re-elected tomorrow, nothing will change," she told reporters at a polling station in Perth's northern suburbs on Friday.
Ms Mettam said the health system was broken, housing was unaffordable and cost-of-living pressures and crime were out of control, as she batted away questions about her predicted loss.
"We appreciate it's a David and Goliath battle, but we're listening to the people of Western Australia," she said.
To win, the Liberal and National parties would need to undo not just their 2021 loss but also Labor's commanding 2017 victory.
Even if the conservatives reclaim every seat lost in 2021, Labor would still be in office with its healthy majority from 2017, when it secured 41 lower house seats. The Liberals won 13 and the Nationals five.
More than 450,000 of Western Australia's 1.86 million electors had cast their pre-poll ballots as of Thursday, according to the state electoral commission.
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