Low voter turnout is expected for the Perth and Fremantle by-elections amid rock-bottom interest after the Liberals didn't bother fielding candidates.
Only 3610 early votes were received for Perth in the first 10 days of pre-polling, down 41 per cent on the same time during the 2016 federal election.
In Fremantle, 3200 early votes were cast by Saturday, down 35 per cent compared to the general poll just over two years ago.
Political analyst Peter Kennedy said those figures pointed to a low overall turnout.
Labor is expected to easily win Fremantle with Josh Wilson, the port city's former deputy mayor who held the seat previously with a 7.5 per cent margin but had to resign over his dual citizenship.
Former state secretary and ex-Kevin Rudd staffer Patrick Gorman is also expected to hold on to Perth for Labor, a seat vacated by lawyer Tim Hammond for family reasons.
The decision to give Labor a free kick - particularly in Perth, which has a margin of just 3.3 per cent - was decried by Liberal Senator Dean Smith as sending a bad message.
Mr Kennedy agreed, saying the Liberals missed a golden opportunity to test their GST reform proposal before next year's federal election.
"They were on the defensive on the GST issue initially and didn't want to put the spotlight on Malcolm Turnbull," he told AAP.
"However their fix has been reasonably well accepted.
"They could have taken the high ground on the GST.
"I think it's a tactical blue."
At the 2016 federal election, the Liberals secured more first preference votes for Perth than Labor and there was an opportunity to reduce that slim margin on Saturday, Mr Kennedy said.
The Liberals justified the no-show by saying contesting the Labor strongholds would waste money better spent on the recent state by-election in Darling Range, a seat snatched back by the conservatives but largely in a Labor backlash.
Mr Kennedy said the Greens should do well again in Fremantle, where the party could benefit from renewed anti-live export sentiment.
And in Perth, independent Paul Collins, a Liberal party member, seems the most prominent opponent for Mr Gorman, who masterminded Labor's thumping state election victory last year.
This campaign has been lacklustre, however, with no big promises made, although Mr Gorman's unusual middle name - Possum - gained some attention.
"I live in the Perth electorate and you'd hardly know it was on," Mr Kennedy said.
