Some 1,500 delegates have gathered in Hanoi for a decisive Communist Party congress amid a febrile political atmosphere unprecedented in recent years.
Social media networks have been awash for weeks with rumours of vicious infighting, letters of denunciation and even a coup, as party factions struggle for primacy.
It marks a startling contrast to the staid and carefully choreographed congresses of the past, which have merely rubber stamped decisions already taken by the Politburo.
All the indications this time point to a dangerous and destabilising deadlock, with the party racked by a clash of wills between two key figures in what is supposed to be a collective and consensual leadership structure.
The two-term Prime Minister, Nguyen Tan Dung, has done little to conceal his ambitions to ascend to the pre-eminent role of general-secretary of the party. The incumbent, Nguyen Phu Trong, has mobilised support in a desperate attempt to block him.
The struggle comes at a key moment in Vietnam’s post war development; balanced as it is between a more whole- hearted embrace of the free market, and a closer political alignment with the United States; and a traditionalist approach based on close ties to Beijing and resolute defence of the party’s monopoly on power.
The 12th Congress begins with a planning meeting, before a formal opening ceremony on Thursday. The delegates will first elect a new central committee, which will then appoint a new general-secretary at the end of the gathering next week.
The internal workings of the Communist Party have always been a taboo subject in Vietnam, and the official media has made no attempt to report the struggle for power.
Vain pleadings by officials that the public should ignore the “poison” being reported on the internet have served only to highlight the party’s inability to hold back a tide of free expression that’s washed away its long held monopoly on information.
Observers say the party’s efforts to pretend that nothing has changed and that “consensus” has been reached in the normal way will
undermine its credibility with a public suddenly exposed to an avalanche of political analysis, speculation and scandal.
Pro-democracy activists and human rights campaigners have been unimpressed by the spectacle.
They see little prospect of political liberalisation, whichever faction of the party emerges victorious.
The prime minister, hailed as a pro-American reformer by some, is denounced by others as an authoritarian crony capitalist.
The incumbent party boss, the guardian of traditional communist ideology and close links with Beijing, cannot be expected to countenance any weakening of the party’s grip on power.
In support of Vietnam’s beleaguered dissidents, Human Rights Watch said the political feuding had served to underscore the inadequacy of an authoritarian political system.
“The future of more than 90 million Vietnamese should not be decided by a small group of communist party officials,” said Brad Adams, Asia director.
“Vietnam should finally adhere to its international legal commitments and allow an election by its citizens instead of yet another selection by the ruling party.”
Much is at stake as the 1,500 delegates gather to make their secretive decisions.
The party may struggle to regain its accustomed consensus after the exposure of such bitter feuding.
The new leaders, once they emerge, will need to confront continuing tensions with China, pressure from the United States on labour reforms and human rights, and relentless demands for economic growth.
They can only look back with nostalgia on the days when stolid apparatchiks could count on absolute compliance from their comrades and acquiescence from an unenlightened populace.