Iran's incumbent president has registered to run in next month's national election, a vote that is shaping up to be a referendum on the landmark 2015 nuclear agreement with world powers.
News reports said Hassan Rohani, 68, submitted the necessary paperwork on April 14, the fourth day of the registration period.
Several high-profile candidates are hoping to challenge Rohani in the May 19 election, including former hard-line President Mahmud Ahmadinejad and his close ally Hamid Baghaei, both of whom filed to run earlier in the week.
But many observers consider Ebrahim Raisi, a hard-line cleric close to Supreme Leader Ayatollah Ali Khamenei, to be Rohani's main rival. Raisi has promised to run a campaign aimed at fighting poverty and corruption in the country.
Ahmadinejad, meanwhile, is best known as a fierce and outspoken conservative whose views on Israel generated international criticism while he was president.
He left office in 2013 amid rumors of a falling-out with Khamenei and with the opposition still simmering over mass arrests and violence in a crackdown following protests over alleged irregularities in Ahmadinejad's reelection in 2009.
Despite the notoriety and popularity of some of Rohani's main challengers, It is unclear whether the Guardians Council -- the agency that vets all candidates before they can appear on the ballot -- will approve the bids.
The council routinely disqualifies those it regards as a threat to the clerical establishment, including unelected officials.
In 2013 the council prevented ex-President Akbar Hashemi Rafsanjani, who died earlier this year, from running again for the same office.
A final list of the candidates cleared to run is due to be released by April 27.
The 2015 nuclear deal negotiated by the Rohani administration lifted crippling economic sanctions in return for Tehran's curbing of its nuclear ambitions.
Since the deal went into effect, Iran has resumed selling oil and signed deals worth billions of dollars to replace its aging commercial airline inventory.
Critics have complained that economic benefits have yet to trickle down to average Iranians.
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