As the merry-go-round of federal leaders making lavish spending promises for Western Australia continued this week, Mark McGowan could barely contain his glee.

"A bidding war for WA is manna from heaven," the WA Premier said.

Mr McGowan was responding to the Coalition's latest bid for WA votes — a $1.6 billion infrastructure package to build new roads, remove level crossings and replace the decrepit Fremantle Traffic Bridge.

But it was not that pledge, in isolation, that had Mr McGowan so excited.

It was the fact that, at the moment, barely a week goes by without either Prime Minister Scott Morrison or Opposition Leader Bill Shorten rocking up to WA with a big bag of cash.

The previous week it was Mr Shorten, promising hundreds of millions of dollars for public transport and making it so a federal Labor government would fund nearly all of the proposed Ellenbrook rail line.

These latest pledges came on top of a long list of infrastructure promises from both major parties, who have now both committed billions to WA across transport, health and other areas.

The Coalition's latest bid for votes included a $1.6 billion infrastructure package. ( ABC News: Jacob Kagi )

A long-term increase to the state's GST share is also locked in place.

The Liberals and Labor will inevitably squabble over who has offered more, who has led the charge and who has shown the strongest commitment to WA.

It will be up to voters to determine the victor of that back-and-forth and, in fact, whether it matters at all.

But for the moment, Mr McGowan and his WA Government look like big winners from this federal campaign.

Commonwealth cash eases WA financial pressure

One of the biggest questions over the WA Labor regime is how they would meet their promise of getting the state's budget back on track, while funding a long list of expensive election promises.

It was a question Mr McGowan faced repeatedly during the 2017 election campaign, when he promised to put billions of dollars towards building new train lines while complaining that the state's finances had been "trashed".

Federal support is not something WA has always been able to count on when building big-ticket infrastructure. ( ABC News: Jarrod Lucas )

But now, even before the federal campaign officially begins, Mr McGowan can rest much easier.

Whether the Coalition is re-elected or Mr Shorten becomes prime minister, a big chunk of the billions required to significantly expand WA's public transport system will be taken care of by Canberra.

That federal support is not something WA has always been able to count on when building big-ticket infrastructure.

The state had to go it alone on projects including the Perth Children's Hospital, Fiona Stanley Hospital and Perth Stadium, with the combined cost of $5 billion an enormous impost on a relatively small budget.

Shorten could become a millstone for McGowan

While the Premier and his budget stand to become significant winners from this federal campaign, it is far from certain he will be spruiking this in two years' time.

The Liberals and Labor will inevitably squabble over who has offered more to WA. ( ABC News: Jacob Kagi )

With the polls pointing to Mr Shorten taking the keys to The Lodge, many Liberals believe that could come with a silver lining for them in WA.

If Mr Shorten wins, he will have been prime minister for nearly two years by the time Mr McGowan faces re-election in 2021.

Liberals are convinced Mr Shorten is unpopular in WA and believe that would only worsen over time.

This is why they are not too concerned about seeing Mr McGowan tying himself so heavily to his federal leader during this campaign.

WA Liberal leader Mike Nahan even publicly declared last week that unpopularity would "rub off" on Mr McGowan.

"Mr Shorten now, and after the election, will be a hindrance to Mr McGowan," he said.

The Liberals are convinced Mr Shorten is unpopular in WA. ( ABC News: Rhiannon Shine )

State politicians often try to distance themselves from matters in the federal sphere, but unpopular national leaders have previously had big impacts on WA campaigns.

The unpopularity of Julia Gillard's government was cited as a key factor in the big margin of Labor's 2013 WA election loss, while Malcolm Turnbull's declining public standing meant his visit during the 2017 campaign was seen by Liberals as unhelpful to their campaign.

Liberals daring to look ahead think that could also be a real factor in 2021, should there be a Shorten government in place.

But Mr McGowan probably won't be thinking about that too much now, as he relishes the buckets of money to be sent his way whoever wins the May election.