With his main rival throwing in the towel, 71-year-old Mr Nguyen Phu Trong is set to continue in the powerful position of general secretary of the Communist Party of Vietnam.
Prime Minister Nguyen Tan Dung, who was widely seen as competing for the post, declined his nomination to the party's central committee - which would have had him in with a chance to be nominated as party chief.
Central committee delegates at the party's eight-day, five-yearly congress, which concludes tomorrow, reportedly approved his withdrawal from the nomination yesterday.
The move surprised analysts. In the lead-up to the congress, even in Vietnam's relatively opaque system, the rivalry between the two men spilt over into social media, with supporters of both trading barbs.
"We don't know for sure why he declined the nomination," saidDr Le Hong Hiep, a visiting fellow of the Vietnam studies programme at Iseas-Yusof Ishak Institute. "He seemed to want the job. About six months ago he was still in a strong position, with a lot of influence in the central committee - but that has declined."
Mr Trong is now seen as staying on unopposed for two to 21/2 years and handing over the position possibly at the party's mid-term conference in 2018. When he first became general secretary in 2011, Mr Trong was widely seen as pro-China. But he paid a historic visit to the United States last year, meeting President Barack Obama in the White House. Mr Obama is expected to visit Vietnam in May.
Mr Trong is also viewed as a conservative, but analysts say that means only that he is cautious on reforms. Under his watch, Vietnam signed a trade agreement with the European Union and signed on to the US-driven Trans-Pacific Partnership.
Vietnam closed last year with fourth-quarter gross domestic product growth at its highest in five years, rising 7.01 per cent, compared with 6.9 per cent over the same period in 2014.
"He is not anti-reform. He takes a prudent approach to reform. He thinks it should be gradual," said Dr Hiep. "Some blame him for a lack of reform, but as party chief his priority would be to maintain the party's rule. If reforms are too extensive or too rapid, they could destabilise the party."
Mr Dung, regarded as a pro-Western reformist but hampered by domestic political weaknesses that left him vulnerable to criticism, is now due to retire. His faction lost to Mr Trong's but he still has allies in the central committee.
There are various factions in the party and there has been a longstanding rivalry between those of Mr Dung and Mr Trong, said Dr Hiep.
"Other factions see (Mr Dung) as corrupt and rent-seeking and a threat to the longer-term survival of the party. They believe that if he rises to the top level, he will expand his patronage network, so they want to block him."
Mr Miguel Chanco, an Economist Intelligence Unit economist based in Singapore, told The Straits Times: "They want stability amid a very volatile geopolitical situation in Asia.
"Some of the outgoing leadership's achievements of the past 12 months have been locked in for the next five years. Regardless of the change in leadership, there will still be elements of market liberalisation."
