Despite having been implicitly advised by Supreme Leader Ayatollah Ali Khamenei not to run, Ahmadinejad on April 12 appeared in the Interior Ministry and signed up for candidacy.
Ahmadinejad's two consecutive terms (2005-2013), the so-called "Ahmadinejad era", were characterized by bad governance, suspected financial irregularities, heavy market intervention, and data rigging.
Stunning Iran and disregarding the words of its supreme leader, former President Mahmoud Ahmadinejad registered Wednesday to run in the country's May presidential election and upended a contest largely expected to be won by its moderate incumbent.
Ahmadinejad, who arrived in the morning in the building of the Interior Ministry in Tehran to accompany his former vice-president Hamid Baghaei during the registration process, made an unexpected move by registering himself as a participant in the upcoming presidential race.
"I repeat that I am committed to my moral promise and my presence and registration is only to support Mr Baghaie", he added without explanation.
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All potential candidates have to be vetted by the Guardian Council and many observers believe Mr Ahmadinejad will not pass this hurdle.
In 2015 Rouhani signed the historic nuclear deal, which may have limited Tehran's nuclear ability but lifted worldwide oil and financial sanctions which had significantly hurt the country's economy. Current President Hassan Rouhani - until now seen as a shoe-in for a second term in office - hasn't even registered for the election yet, though 197 other hopefuls have.
While conservatives are anxious that Mr Ahmadinejad or Mr Baghaei's presence might split their votes, allies of Mr Rouhani are also concerned about the attractiveness of populist candidates with nationalist anti-establishment slogans. Iran insists its nuclear program is for peaceful purposes. The council is typically responsible for disqualifying the majority of registrants for making it to the final candidates list. U.S. President Donald Trump, a staunch critic of the nuclear deal, could move to dismantle it, particularly if a hard-liner like Ahmadinejad is elected.
"Although it is quite possible that Ahmadinejad will be disqualified by the Guardian Council, this could turn out to be politically messy for them", said Sabet.