Harare - Only if other high profile members of Zimbabwe's ruling party desert President Robert Mugabe might the scales tip against the veteran leader at March's election.
The defection of politburo member Dumiso Dabengwa at the weekend to join the presidential campaign of former finance minister Simba Makoni has certainly rocked Zanu-PF.
But political analysts believe Mugabe, 84, can still beat a divided opposition despite economic turmoil that has left Zimbabweans struggling with shortages of food, fuel, water and power as well as the world's highest inflation.
"The fight is still going on, it's getting exciting but I think it would be foolish and very premature for anyone to write off Mugabe yet," said John Makumbe, a political commentator and fierce Mugabe critic.
Mugabe, who has ruled since independence from Britain in 1980, faces his biggest challenge to power from Makoni - now expelled from Zanu-PF - and long-time opponent Morgan Tsvangirai.
Dabengwa called Makoni's bid for the March 29 election a rescue operation for the country of over 12 million, where many blame government policies for the economic disaster.
Political analysts said that although Dabengwa could mobilise some support for Makoni in his restless native southern Matabeleland province, the former guerrilla commander's political clout was already in question there after losing parliamentary elections twice in the last eight years.
Matabeleland has long been a stronghold of the opposition, mainly over simmering anger stemming from a government crackdown against an insurgency in the 1980s, which human rights groups say killed thousands of people.
Dabengwa - a former intelligence chief in Joshua Nkomo's Zimbabwe People's Revolutionary Army (ZIPRA) during the 1970s independence struggle - has also been involved in a turf war with veterans backing Mugabe's bid for re-election.
Affectionately known by his guerrilla name "Black Russian" under his comrades, Dabengwa lined up with a number of former senior ZIPRA fighters to publicly back Makoni on Saturday.
"There is no doubt this is a big blow against Mugabe, but on its own, and measured against the hesitancy we are seeing in other officials in Zanu-PF, and measured against other senior officials coming out in support of Mugabe, it's not a knockout blow," said Eldred Masunungure, a political science professor at the University of Zimbabwe.
"I think a really devastating blow would be the defection of several top officials, including those generals the (local) media has linked to Makoni," he said.
Makoni has long said his campaign had the support of several senior Zanu-PF officials, but they have not come out openly. In fact, many top officials have gone to pains to make public their support for Mugabe.
Local media have suggested that Makoni is working with former army general Solomon Mujuru, an influential but reclusive figure in the ruling party. Mujuru - whose wife is a vice president to Mugabe - has not commented on these reports.
Both Makoni, running as an independent, and Tsvangirai, who leads the biggest faction of the divided main opposition Movement for Democratic Change (MDC), say Zimbabweans cannot afford Mugabe's rule any longer.
Makoni and Tsvangirai have failed to forge an anti-Mugabe alliance, however, leaving him in a strong position even without added advantages such as controlling the security forces and state media.
Mugabe, who has branded Makoni a political prostitute, has not yet publicly commented on Dabengwa's defection but his spokesperson George Charamba dismissed it as insignificant.
"What is Dabengwa worth by way of supporters. He brought none to Zanu-PF, he takes none to the independent."
(Editing by Marius Bosch and Matthew Tostevin)
(For full Reuters Africa coverage and to have your say on the top issues, visit: http://africa.reuters.com/ )