For the many who have pinned their hopes on Sam Rainsy and Kem Sokha’s Cambodia National Rescue Party, it would be a crushing blow for the delicate alliance to have come so far only to split now.

Yet less than six months from the June 4 commune elections – the most important test yet of the nearly five-year-old experiment in placing the downfall of Prime Minister Hun Sen ahead of competing egos – the still-maturing marriage of convenience has never been so openly fractious.

From Sokha’s open rebuke of Rainsy’s refusal to leave the safety of Europe, to Rainsy’s obvious displeasure in giving up the title of parliamentary “minority leader” for Sokha, never before have the deep personal differences in the CNRP appeared so at risk of blowing up. (Last month, Sokha’s daughter even publicly taunted Rainsy as “Peter Pan” for his perceived childishness.)

It’s a familiar place for Hun Sen, who over his three decades in power made a name for himself as Cambodia’s great divider – slicing and dicing the Khmer Rouge, the Khmer People’s National Liberation Front, Funcinpec and anyone else who dared oppose him. So there is a wealth of experience for Sokha and Rainsy to draw on as they perform their latest three-person dance with the man they have sworn to remove from power by working together.

“I hope the two leaders will not fall into that trap again,” said Son Soubert, who has for legal purposes served as nominal leader of Sokha’s old Human Rights Party since its structure and membership was merged with that of Rainsy’s party to form the CNRP in July 2012.

“If they have learned from the past, this is what the prime minister has done: First, the CPP divided the KPNLF, and when they succeeded, they started to do it with Funcinpec, too. Now – I hope – the political parties should have learned their lesson,” he added.

However, Soubert, who is a former member of the Constitutional Council and son of late prime minister Son Sann, said that even though he has known Rainsy and Sokha for decades, he could not predict if the former fierce rivals could prove themselves different to past leaders.

“That is difficult to say. Human nature is that they both have reason – to think and to calculate – but they have also their egos and hearts,” Soubert said.

Both CNRP leaders should also be intimately aware of the relevant history, with Rainsy having his political roots in Funcinpec – for whom he was finance minister in the 1990s in coalition with the CPP – and Sokha having cut his teeth as a clandestine KPNLF operative in the 1980s.

Outside of its large youth following, the CNRP in fact still remains largely a latter-day regrouping of holdouts from both those movements, which had been both allies and rivals from their creation to their collapse at Hun Sen’s hands. And much of that divide remains.

The Sam Rainsy Party faction of the CNRP remains associated with the remnants of Funcinpec, from which the SRP split in the 1990s, as well as Rainsy’s personalist style, while Sokha’s HRP is heavily populated by former KPNLF figures, who touted their old party as more democratic.

As a founding Funcinpec member who now sits in Sokha’s faction and often criticises Rainsy, Prince Sisowath Thomico bucks that trend. He said that for all the personal differences between Rainsy and Sokha, he believed both were hyper-aware that they cannot win alone.

“I’ve said this many, many times before: Kem Sokha and Sam Rainsy cannot be divided, because if they split, they will both have no future. The CNRP has raised so much hope, so I do not believe in divisions between Sokha and Rainsy,” Thomico said.

“But what I am more concerned about,” the prince added, “is divisions between their supporters – not at the grassroots, but at the intermediary level. We have to remember that the CNRP is still a union of the Sam Rainsy Party and the Human Rights Party.”

“Both parties had different ethics, different organisations and different cultures,” he said. “At the moment, some SRP people could feel offence.”

Still, few among the factions around Rainsy and Sokha should be tricked by Hun Sen suddenly favouring one and excluding the other, given the brazenness of the gambit, said Sophal Ear, an associate professor at Occidental College in Los Angeles.

“It’s like Theresa May (Conservatives) saying she doesn’t want to work with Jeremy Corbyn (Labour) anymore and he must be replaced in the UK Parliament,” said Ear, who wrote Aid Dependence in Cambodia: How Foreign Assistance Undermines Democracy.

Such a proposal could only be interpreted as an undisguised tactic to secure unfair political gains, he said, and so would dupe few among the opposition. “On the flip side,” Ear added, “the optics are damaging for the CNRP: real or apparent loss of agency.”

CPP spokesman Sok Eysan said that while he did not want to say his party was using tricks to divide the CNRP by pampering Sokha and excluding Rainsy – after doing the opposite throughout 2015 – he would also feel uncomfortable denying it.

“If we completely deny this, that would also not be reasonable, because generally, for competing parties in a democratic society, there is no party that wants its competitor to become stronger,” Eysan said. “It’s the same for any party, not only the CPP.”

“Any party that is created wants its competitor to become weaker, and this is normal,” he reiterated. “If we deny it completely, it would seem to contradict the truth.”

While a prime minister selecting his own opposite would seem ridiculous in most countries, for Hun Sen, it is just another page from a well-worn recipe book of divide-and-conquer.

He split Funcinpec in the 1990s and 2000s by declaring he would only work with minor official Ung Phan – and later Ung Huot, and later Nhek Bun Chhay – and not the party’s leader, Norodom Ranariddh. He split the KPNLF by saying that he would work with Ieng Mouly, but not party leader Son Sann.

However, Soubert, the nominal president of Sokha’s old HRP, said that he believed the deputy opposition leader’s unexpected rapprochement with Hun Sen was not the past repeating itself, but instead a necessity while the CNRP has a chance to extract more from Hun Sen.

“Now, the concern of Kem Sokha is the people from the party and NGOs who are in jail from his case,” Soubert said, referring to four Adhoc rights workers and an elections official who remain in jail over the “prostitution” case for which Sokha was pardoned. “When they are released, we will see.”

Rainsy said in an email that he indeed could see the old tactics of division behind Hun Sen shifting his affections to Sokha and his disdain to Rainsy, but also appeared to reserve judgment on the matter.

“You are possibly right,” Rainsy wrote. Asked why he believed Hun Sen would be so transparent in trying to split him from Sokha, Rainsy added: “Because the game has become so obvious that any cover would be useless. Worse, the guy has no other game to play.”

Indeed, while Hun Sen may revel in the politics of division, it has been rare for him to leave success to so late in the game – especially with Rainsy and Sokha seeming only to grow more sure-footed as their party unity holds up amid their public divisions.

Before the CNRP, Hun Sen had never faced a united opposition at an election, and success for the CNRP in the commune elections in six months would send shivers down the premier’s spine as he ponders how to protect the veneer of invincibility he has curated.

With the be-all-and-end-all July 2018 national election scheduled only a year after the commune poll, a question that has over the past few years seemed easy to kick down the road has suddenly arrived to demand a answer: Can Hun Sen break the CNRP?

ADDITIONAL REPORTING BY MECH DARA