Only three weeks ago the Liberals appeared to be in a sweet spot in WA, as then-prime minister Malcolm Turnbull visited Perth to spruik his Government's proposed GST fix.

WA's federal Liberals looked visibly relieved to finally have a proposed deal to deliver the state a fair share of GST revenue and combat growing voter anger over the issue.

At a press conference where he had flanked Mr Turnbull, marginal seat holder Christian Porter — a senior Minister in the Federal Government — could not contain his delight.

"People love it. There's finally a fix," he declared.

Fortunes now favour Labor

Fast forward to this week and the tables appeared to have turned, as federal Opposition Leader Bill Shorten campaigned in Perth for two days — his sixth visit to WA this year.

Mr Shorten had a spring in his step and appeared relaxed as he went from marginal seat to marginal seat selling Labor's alternative GST offer.

And he did not miss any opportunity to remind voters of the recent Liberal leadership turmoil in Canberra that resulted in Mr Turnbull being dumped as PM in favour of Scott Morrison.

His press conferences were littered with references to the "instability", "chaos" and "division" within the federal Liberal ranks as he painted his team as united and ready to take office.

"We're ready whenever the election's called, we're ready because for five years we've been the stable party of Australian politics, we're ready because not only are we united but we have a preoccupation with policy," he said.

Mr Shorten also tapped into public sentiment by making repeated references to the fact most WA federal Liberal MPs backed Peter Dutton over their state colleague Julie Bishop to be prime minister — a move that resulted in her decision to resign as foreign affairs minister and consider her political future.

Ms Bishop announced she was resigning just hours after some of the tactics used to knock her out of the leadership race were revealed.

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"She served Australia with some flair, a bit of panache … no one could argue with that, but it would appear that no other WA MP in the Liberal Party voted for her and that to me speaks volumes," Mr Shorten said.

"What message are we sending to West Australians that your number one, your most senior West Australian, who's undoubtedly been good for raising funds for the party and representing Australia on the world stage — when it comes to the tough business she was left friendless."

Julie Bishop was deserted by her fellow WA Liberal MPs in the leadership vote. ( AAP: Lukas Coch )

While in Perth, Mr Shorten pledged that if he won the next federal election Labor would legislate a 75 cent GST floor within 100 days of coming to office.

Since being elevated to the role of Prime Minister, Scott Morrison has confirmed the proposed GST fix he announced as treasurer, which would deliver WA an extra $4.7 billion over eight years, remains on the table under his new Government.

While the Liberals have made much of the fact Mr Shorten has so far refused to commit to following their pledge to change the GST distribution formula, ultimately it will be WA voters who decide which party is offering the better GST deal.

Premier Mark McGowan has refused to be drawn on his preferred proposal and has instead enthusiastically backed both.

A poll nightmare in WA

While the Liberals' proposed GST fix may have dampened growing voter anger over WA's low share, recent opinion polls appear to indicate the leadership crisis has taken a toll on the Government's stocks.

A Newspoll taken just after the recent Canberra leadership bloodletting showed Labor leading the coalition 56 per cent to the Government's 44 per cent on a two-party preferred basis.

It also showed Mr Shorten as more popular than Mr Morrison (39 to 33 per cent) after the Labor leader trailed Mr Turnbull in the previous poll by 12 points.

The ousting of Malcolm Turnbull appears to have cost the Liberals dearly in WA. ( ABC News: Matt Roberts )

West Australians may like the Liberals' GST offer, but the outpouring of public anger online and on radio talkback in the past week shows voters are generally disgusted when a sitting prime minister is knifed by their own party.

They also bristle when they witness politicians talking about themselves, rather than getting on with the job taxpayers pay them to do.

Just ask Labor about their own demise under the tumultuous Rudd/Gillard/Rudd years in government.

At the 2013 WA state election, the Liberals capitalised on Labor's turmoil at a federal level by running a highly successful negative ad campaign that simply said "Labor's a mess".

It helped secure then-premier Colin Barnett a second term in office because it successfully tapped into voter anger over federal Labor's chaos and dysfunction and painted them as unfit to govern.

Campaigning on merits, not resentment

Mr Shorten's pitch to WA voters this week, as he toured marginal seats in Perth's eastern suburbs with Labor's candidates for the next federal election, appeared to be straight from the same playbook.

There is no doubt the recent events in Canberra have provided Labor with plenty of fodder to run its own negative campaign ads at the next federal election, painting the Liberals as a mess.

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But Mr Shorten was at pains to argue he wanted to win over voters with more than just that.

"Last week was not a good high point for the Liberal Party … but what I'd promise Australians is that I'm not complacent," Mr Shorten said.

"I don't assume that just because there are negatives with the Government and their chaos and division, that's not the reason I say vote for us. I say we want to earn your respect by making good announcements."

Mr Shorten may argue that, but the Liberals' implosion at a federal level certainly appears to have turned the party's sweet spot in WA sour very quickly and left a bad taste in the mouths of many voters in the west.

It would be a welcome turn of events for any opposition leader in the lead up to an election.