Former African Union chairman Jean Ping, a leading critic of Gabon's President Ali Bongo, says he will run for president this year, hoping to break the ruling party's near 50-year grip on power.
Ping also told Reuters in an interview he wants to make the presidency more accountable, institute term limits, and invest in health, education and infrastructure.
Bongo, the son of long-ruling former president Omar Bongo who won a disputed election in 2009 after his father's death, is currently favoured to win the August election and secure a second mandate to rule the Central African oil producer.
But analysts say Ping, a leading critic of the Ali Bongo, might be able to capitalise on falling oil prices and broader frustration over wealth inequality, despite the ruling PDG party's traditional advantages such as a strong patronage network.
"I am committed to defending the rights of the Gabonese and I will go all the way to victory," Ping told Reuters after a meeting with supporters this weekend, announcing plans
The 73-year-old one-time ally of Omar Bongo has been at loggerheads with Ali Bongo since youths attacked his house with rocks a year ago.
Ping accuses a Bongo presidential aide of organising the attack, although the government has vigorously denied this and a court has since ordered Ping to pay 650 million CFA francs ($1.07 million) in damages.
If elected, Ping says he would reinstate a 1991 constitution shortening the presidential mandate from seven to five years, bring in term limits and implement a two-round election system.
"It is broadly accepted today that you can't have more than two mandates," said Ping. "The President should not be a demigod."
Gabon's current one-round system, an exception in the Francophone countries, is seen as favouring the ruling party since it requires strong unity among the opposition from the start rather than after a first-round when the numbers running have been cut to two.
Members of the United Front of the Gabonese Opposition, an alliance of Bongo opponents, could in theory still reject Ping's candidacy and some have grumbled over whatr some see as efforts to muscle his way to the top.
But Roddy Barclay, head of intelligence and analysis at London-based consultancy africapractice said that was unlikely.
The small former French colony is one of Africa's richest countries, producing around 230,000 barrels per day of oil and classified as an upper middle-income nation by the World Bank. However, most of the wealth is concentrated among elites.
Sharp falls in oil prices have prompted the cabinet to trim budgets and Bongo's government faced violent protests a year ago over a range of grievances and trade union disputes. ($1 = 605.2900 CFA francs)