Federal Labor leader Bill Shorten has campaigned in Perth with Mark McGowan, his third visit on the hustings compared to Prime Minister Malcolm Turnbull's sole trip west.
Two polls released on Saturday pointed to a better-than-expected 11 per cent swing to WA Labor, giving the party 14 extra seats.
That's more than enough, given the opposition needs 10 seats on a 10 per cent swing to seize power, which has never been done before in the state.
After casting his vote with his wife Sarah and three young children, a smiling Mr McGowan said he felt terrific and not nervous on Saturday.
"I think we've done our absolute best to present a good alternative to the people of Western Australia," he told reporters in his electorate and home suburb of Rockingham on Perth's southern fringe.
"It's now up to the voters but I certainly hope this evening we see a change of government because I think that's what Western Australia needs."
Asked about the prospect of dealing with a messy upper house if Labor won, he said the party had never controlled the upper house in WA in 117 years "so we're pretty used to having to deal with an upper house which we don't have the numbers in."
He held a second press conference with Mr Shorten in Yokine in Perth's inner north, which is in the Mt Lawley electorate held by Liberal Speaker of the Legislative Assembly, Michael Sutherland.
"I know that West Australians need something better than what they've had and in Mark McGowan, they're going to get that outcome if they vote for him today," Mr Shorten said.
He took aim at Mr Turnbull for not showing up in Perth again after his visit last month, which was considered a massive flop because he didn't give any commitments after promising in August to introduce a "floor" to the GST below which no state or territory's share can fall.
"I'm sure Mr Turnbull will be sitting somewhere tonight, watching the results come in from Western Australia ... with a very nervous eye," Mr Shorten said, linking the vote to the recent penalty rates decision.
Mr Shorten also described the WA Liberal preference swap deal with Pauline Hanson's One Nation as "the ultimate exploding cigar of this election".
"And I have to say I think Malcolm Turnbull has been too weak in not stopping it," he said.
"We've made it clear, both Mark at the state level and myself at the national, nowhere anywhere will Labor preference One Nation and we think Malcolm Turnbull's let himself down here."
West Australian Premier Colin Barnett is joined by his wife Lyn Barnett to cast his vote. Source: AAP
Barnett says he is preparing for WA win
WA Premier Colin Barnett has admitted to feeling some nostalgia about his 27 years in parliament as he voted in Perth because, win or lose, he will stand down during the next term.
Mr Barnett voted with his wife Lyn in his Cottesloe electorate, saying it was still exciting to see his name on a ballot and he was optimistic despite two newspaper polls on Saturday putting Labor ahead 54-46 two party preferred.
"I don't brace for a loss I always prepare for a win," he told reporters.
