A former army officer who led a brief revolt against Peru's government in 2000 has officially registered to run in presidential elections next year.
Ollanta Humala has promised to cut the presidential salary
Recent opinion polls have shown growing support for Ollanta Humala, who has argued for a nationalist energy policy.
Mr Humala was forced into exile and retirement after a revolt against former President Alberto Fujimori.
Correspondents say he is similar to leftist Venezuelan head Hugo Chavez, who also led a failed military coup.
Mr Humala has said he is outraged at the way some of Peru's traditional parties are exploiting a current debate over pardoning military officers blamed for human rights abuses in the fight against Shining Path guerrillas in the 1980s and 1990s.
Brothers in arms
Mr Humala will lead the Peruvian Nationalist Party to the polls on 9 April next year.
He has called for tighter central control over Peru's energy assets and has pledged to cut the presidential salary.
The former army lieutenant colonel has also said he will introduce what he describes as a more participatory form of democracy and will limit investment in Peru by companies from Chile.
Peru lost land to Chile in a19th century war and some in Peru still regard their southern neighbour as an arch-rival.
Mr Humala's brother, Antauro, also a former army officer, is currently in jail for leading an armed uprising against the government of President Alejandro Toledo earlier this year.
Some have argued that the January 2005 uprising in an Andean town was designed to boost Ollanta Humala's bid for the presidency.
Whatever the motive, correspondents say, rebels like the Humala brothers hold an obvious appeal for an underclass still searching for a solution to the hardships of life in Peru's impoverished hinterlands.