Such is the level of bitterness from Vince Catania's decision to abandon the Labor Party that, more than 10 years later, he inevitably has abuse hurled his way every time he stands up in State Parliament.

"He has behaved as an immature and petulant young man, with a short-term solution, an easy ride in politics and hasn't had the ticker to defend a marginal seat," then Labor leader Eric Ripper said on the day in 2009 that Mr Catania defected to the Nationals.

"What he has done is betray the people of the North West, those people voted for a Labor member."

Many Labor MPs are still bitter about Vince Catania's decision a decade ago to leave the party. ( ABC News: Eliza Laschon )

Mr Ripper's level of anger on that day has never died down within the Labor camp, with the common refrain that Mr Catania is a "rat" for jumping ship reflecting a level of hatred between MPs rarely seen in WA politics.

It was a similar story when former police minister Rob Johnson fell out with the Liberal Party and became a fiercer critic of Colin Barnett than even Labor was.

The level of vitriol was so high then that, after Peter Katsambanis beat Mr Johnson to the seat in 2017, he left a 3:00am voicemail message on his opponent's phone that left no doubt about the extent of the ill-feeling.

"Hello Rob, this is Peter Katsambanis calling. Have a great day. Enjoy the rest of your life," Mr Katsambanis said.

There was no love lost between former Liberals Peter Katsambaris and Rob Johnson. ( ABC News: Eliza Laschon/Andrew O'Connor )

Vitriol gives way to a love-in

But the reactions of the scorned parties in those examples, plus cases like those of John Bowler and John D'Orazio, look like a parallel universe compared to the relative love-in of Geraldton MP Ian Blayney's defection from the Liberal Party this week.

There were no public expressions of anger, no accusations of ratting, and nothing but best wishes from Liberal leader Liza Harvey on Mr Blayney's attempt to jump to the rival Nationals.

"I have a very high regard for Ian and he is a friend," Ms Harvey said.

She described Mr Blayney as a good MP and maintained she "respected his decision" to abandon the Liberal ranks.

Mr Blayney's departure is not a good look for Liza Harvey days from the WA Liberal conference. ( ABC News: Andrew O'Connor )

Mr Blayney went even further, saying: "We remain good friends and I think if she is given the opportunity she will be an absolutely outstanding Premier".

But the fact there were no public displays of ill-feeling likely left many Geraldton voters scratching their heads, trying to work out why an MP they voted for three times under the Liberal banner now wants to join a party he fought bitterly against two years ago.

Mr Blayney said he wanted to spend more time focused on regional issues, but it is likely he could have done so under a Liberal banner.

He downplayed the impact of being stripped of the agriculture portfolio in the latest shadow cabinet reshuffle, portraying it as only a minor factor.

But Liberal MPs Mr Blayney spoke to in the lead up to his announcement have a different version of events.

"That is bullshit," one said this week.

Confusion around motive remains

The key factor, according to Mr Blayney, was the 2017 election campaign and what he saw as a lack of help in a fight where he barely held on.

"I got not very much support and it really took its toll," Mr Blayney said this week.

Ian Blayney says Ms Harvey would make an outstanding premier, given the chance. ( ABC News: Chris Lewis )

Mr Blayney went into that campaign with a 22.8 per cent buffer over Labor and the Liberals were desperately trying to hold on — unsuccessfully it turned out — to more than a dozen at-risk seats with smaller margins, which perhaps gives some context as to why their campaign was more focused elsewhere.

And he did get some help too, with Mr Barnett coming to town with a $140 million promise for a hospital upgrade during the campaign.

It all left a few Opposition MPs rather confused as to how Mr Blayney had decided to jump to a party he once publicly described as "chauvinistic" and "very offensive".

And those comments appear measured compared to much stronger feelings of resentment Mr Blayney conveyed about the Nationals during Liberal partyroom meetings over the years, according to accounts from MPs who were present.

Adding to the confusion for some was why an MP, who only ever got into State Parliament because of the Liberal brand, was able to desert without a single cross word being said about him.

It will give Liberal MPs and party members plenty to chat about, when they gather for their state conference in Perth this weekend.

As for the broader picture, Ms Harvey's measured response to Mr Blayney's defection was seen as an attempt to downplay the impact of one member of her team jumping ship.

But, whatever the reasons, losing an MP — when the Liberals had so few to begin with — less than two months after she became leader is unlikely to be seen as a great look for Ms Harvey.

