Former federal minister Stephen Smith's challenge for the West Australian Labor leadership is all but over after the majority of party MPs backed incumbent Mark McGowan.
Shadow cabinet - representing 21 out of 32 Labor MPs in the WA parliament - unanimously threw their weight behind Mr McGowan at a meeting on Monday and Mr Smith conceded caucus would probably follow suit.
"That makes a comparable decision by the state parliamentary Labor party tomorrow inevitable," the former foreign and defence minister said in a statement.
A caucus meeting is scheduled for Tuesday, when backbenchers will also have their say.
Mr Smith formally declared on the weekend he would challenge Mr McGowan if he had the backing of most of the party, saying he'd been approached by both front and backbenchers who believed the party couldn't achieve the 10 per cent swing needed to prevent the government of Colin Barnett winning a third term.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Mr Smith dismissed a Newspoll in January that put Labor in an election-winning position, saying no one believed it.
Several Labor MPs labelled Mr Smith disloyal and said he would damage the party's chances at the 2017 election.
Albany MP Peter Watson was particularly scathing, saying those who had encouraged him had "duped him" into thinking he had the numbers to succeed.
Several MPs AAP spoke to said Mr Smith had never spoken to them about challenging.
"I don't know how this could be done without Labor killing itself ... if he had a methodology or strategy I don't know what it is," said one.
After shadow cabinet voiced its support for Mr McGowan, the Labor leader vehemently defended his position, saying the matter was "now over".
"I think Mr Smith has got the message," he told reporters, reiterating he totally believed he would take the party to the next election.
Political analyst Peter Kennedy said the turn of events looked good on the surface for Mr McGowan, but may well not be the end of the matter.
"Knowing Mr Smith's track record ... I'd be surprised if it all folded up quickly," Mr Kennedy said.
On Sunday, Mr Smith flagged his interest in the seat of Baldivis in Perth's south, which Mr McGowan has earmarked for his senior media adviser Reece Whitby, who previously lost twice in Morley.
There has been speculation Mr McGowan's supporters will try and rush through the pre-selection process in a day or two instead of over a fortnight to shut out Mr Smith, which he said would "reek of panic and desperation".
Federal ALP Member for Perth Alannah MacTiernan urged Mr Smith against "biding one's time on the bench until another call comes".
"He believes that he's got something to offer, an X factor that he can bring to the show," she told reporters.
"OK, so be it. But let the caucus decide. Let that be it."
