Liberal pre-selectors have dumped West Australian MP Dennis Jensen as the candidate for Tangney after extracts from a novel he wrote containing graphic sex scenes were publicly leaked.
His challenger, former state Liberal director Ben Morton, won preselection 57 votes to seven on Sunday, but the decision will still need to be ratified by State Council next weekend.
The result comes despite Dr Jensen having the support of Prime Minister Malcolm Turnbull, who recommended Dr Jensen be re-endorsed for the safe Liberal seat, which he has held since 2004.
Dr Jensen made headlines last week after it was revealed that several years ago he pitched his fictional novel to a publisher using his parliamentary letterhead.
He admitted it was a mistake but questioned the timing of the leak ahead of the preselection battle.
After the meeting on Sunday Dr Jensen told AAP the story, published in The Australian newspaper, "absolutely" affected his chances of being re-endorsed and was part of a "deliberate strategy" to put his supporters offside.
Dr Jensen said he had enlisted defamation lawyer Martin Bennett to commence proceedings against the newspaper in the WA Supreme Court on Monday.
There have been two previous attempts to oust Dr Jensen - he was saved once by former prime minister John Howard and another time by State Council.
He conceded it was unlikely a challenge against this preselection decision would succeed given it was such a strong vote against him.
Mr Morton told reporters he was proud and humbled that the Liberals had put their faith in him and thanked Dr Jensen for his contribution to the party and the community.
Premier Colin Barnett said Mr Morton had an "enormous amount of ability" and did not doubt he would succeed.
Controversy has followed Dr Jensen recently after he lashed out over indigenous welfare programs, saying taxpayers should not fund "noble savage" lifestyle choices of remote communities.
He is also an outspoken climate change sceptic and opposes same-sex marriage.
