Three men will challenge Yoshihiko Noda for leadership of the governing Democratic Party of Japan, it was announced yesterday, with the prime minister widely expected to survive the vote.
Under party rules, there must be an election every two years for the job, which currently comes with the post of premier, but after his only serious rival ruled himself out, Noda's grip looks secure.
As prime minister and leader of the DPJ - presently the biggest party in parliament - Noda has pushed through unpopular legislation on doubling sales tax.
This, alongside general disenchantment with his once-popular party, has left many lawmakers fearing for their jobs in the general election expected by the end of this year.
"I decided to run for the party presidential election as I can't abandon the task of rebuilding the party and revitalising Japan," Noda said as all four candidates gathered in Tokyo.
He admitted that in the 12 months since he became prime minister - at the time the sixth man in five years to do the job - the already ill-disciplined DPJ has disintegrated further. "We have been able to overcome a huge mountain with legislation for the reform of social security and tax, but many members left the party and we are still suffering from that."