Feelings in PKR have been simmering, especially after the bombshell dropped by DAP leader Anthony Loke earlier this week.
The PKR rank-and-file were riled by the way Loke criticised Datuk Seri Anwar Ibrahim for being indecisive as well as the fact that their partners DAP and Amanah seemed to be supporting Tun Dr Mahathir Mohamad as the prime minister (PM) candidate.
They felt betrayed and yesterday, the pot came to a boil.
The PKR supreme council and MPs decided at a special meeting that they do not accept Dr Mahathir as the PM candidate and that their party president is their choice for the top job.
The party also remains committed to Pakatan Harapan and its aspirations for change and the betterment of the country.
PKR's loyalty to Anwar for the PM post is not new but the decision is coming at a critical junction with Dr Mahathir trying to make a second comeback as PM.
The other thing is that Pakatan is trying to retake Putrajaya and needs a PM candidate who can bring in the numbers to make that happen.
"Yes, we want Anwar as the PM candidate. But more important than that, our party does not trust Mahathir anymore. We don't want him back.
"We have been twice bitten. People will laugh at us if we get bitten a third time," said PKR vice-president Chang Lih Kang.
Chang, who is also Tanjung Malim MP, admitted he was shocked to see Loke support a formula where Dr Mahathir would be PM for six months before handing over the reins to Anwar.
"All this while, we thought our friends in DAP and Amanah were with Anwar," he said.
The fight over the PM post that hastened the fall of the Pakatan government has resulted in a deep split in the coalition that will hinder its ability to take on its real enemy, Perikatan Nasional.
A string of high-level meetings between Pakatan, Warisan and Dr Mahathir to settle the question of who ought to be Pakatan's PM candidate not only resulted in a stalemate but widened the cracks in the Opposition front.
Loke is a rising star in DAP and Anwar did not respond immediately to what Loke said about him.
But the Opposition leader reacted with a classic metaphor - he tweeted pictures of himself pruning the bamboo plants in his Bukit Segambut home with the caption: "Cantas apa yang patut" (chop off what is necessary).
His party took the cue and a day later, PKR's highest decision-making body unanimously rejected Dr Mahathir as the PM candidate.
Actually, as Chang indicated, this has been the prevailing sentiment in the party all along but it is finally out in the open and in clear-cut terms.
"For some of us, it is better to be in the Opposition than in a government with Mahathir," said Chang.
The latest development is going to be awkward for Pakatan in the days ahead and raises so many questions.
For a start, how will Dr Mahathir take the rejection?
Malaysia's grand old man is used to having his way. Everyone has seen how he can damage those who do not do what he wants.
Dr Mahathir may have only five MPs but he has an indomitable will and an enormous personality. He knows how to make waves with his words and action.
Nevertheless, it is a blow to Dr Mahathir going into the July meeting of Parliament.
Dr Mahathir's motion of no confidence against the Prime Minister is still pending. Given the way the MPs in PKR feel about him, the motion is as good as dead in the water.
Dr Mahathir and Anwar keep saying they have no issues with each other but the point is they have problems accepting each other.
"It's going to be a rough ride ahead," said former DAP MP Jeff Ooi.
PKR's decision also puts DAP and Amanah in an awkward spot.
Can things be the same again for the Pakatan partners given that DAP and Amanah appear to be defending the Mahathir option?
DAP, said Ooi, may have overplayed its hand at pressuring Anwar to accept Dr Mahathir as the PM candidate.
Dr Mahathir is known as "Lao Ma" (old horse) among the DAP crowd and the horse took them to victory. But it suddenly bucked and threw them off, yet they want to climb back on again.
"My sense is that it was of utmost importance for DAP to get back to power at all costs. They think that Mahathir can get them the Malay support.
"But why must DAP be the one to shake the tree knowing that the Chinese are no longer comfortable with Mahathir?" said Ooi.
PKR information chief Datuk Seri Shamsul Iskandar Mohd Akin pointed out that although Dr Mahathir insisted on making a comeback, he always spoke softly and in measured tones during meetings.
"He was never aggressive, he did not raise his voice even though we know he would not back down.
"We are not sure what he will do but this is the chance to make a fresh start. It is time for Mahathir to support Anwar," said Shamsul.