Associated Press journalists watched as stunned election officials processed Ahmadinejad's paperwork on Wednesday. "Even (former hardline president Mahmud) Ahmadinejad had more experience and he was disastrous for the economy", said reformist Tehran-based economist Saeed Laylaz.
Ardavan Amir-Aslani, a French-Iranian lawyer who advises European companies setting up in Iran, said he would be surprised if Rouhani does not win re-election despite the economic malaise. In fact, however, it was probable that he could give way to his political colleague, former Vice-President Hamid Baghaee, to run on his platform, although there seems little likelihood that the Ahmadinejad camp could win.
Influential Shia cleric Ebrahim Raisi, an ally of Supreme Leader Ayatollah Ali Khamenei, appears to be the leading hardline candidate so far.
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.
Seen as a proxy for Ahmadinejad after the former president was told not to stand by the supreme leader.
In September 2016, local media quoted Iran's Supreme Leader as saying that "I do not find it advisable that you (Ahmadinejad) participate" in the next presidential elections.
His father-in-law leads Friday prayers in Mashhad and both have seats on the Assembly of Experts that will choose the next supreme leader - a position for which Raisi himself is often rumoured to be in the running. After leaving the office of President in 2013 at the end of two controversial terms, the firebrand populist has been largely inactive in politics. Iran's economy also suffered under heavy worldwide sanctions during his administration because of Western suspicions that Tehran was secretly pursuing nuclear weapons.
Besides, the nuclear agreement with powers in July 2015 was instrumental to alleviate the risk of war against Iran, he said.
Internationally, Ahmadinejad is more known for repeatedly questioning the scale of the Holocaust, predicting Israel's demise and expanding Iran's contested nuclear program.
Every president since the early 1980s has won a second term, and Rouhani has done much to maintain his alliance of moderates and reformists - stabilising the economy and signing a landmark nuclear deal with world powers that ended many sanctions and promised a fresh start with the global community.
Iran's Defense Minister Brigadier General Hossein Dehqan (1st L) briefs President Hassan Rouhani (C) on a tactical domestically-built drone, dubbed Mohajer-6, in Tehran on April 15, 2017. The council normally does not approve dissidents or women.
"From now on, protecting the deal is one of the most important economic and political issues", he said of the nuclear deal. Iran has since resumed selling oil and signed deals worth billions of dollars to replace its aging commercial airline inventory. The benefits have yet to trickle down to the average Iranian, though, fueling some discontent.
Iran's President Hassan Rouhani has submitted his name for candidacy in this year's presidential election. Rouhani also is presumed to maintain support among liberals and those wanting tensions eased with the West, though polling is hard. If you would like to discuss another topic, look for a relevant article.
Human rights campaigners say there have been few, if any, moves to bring about greater social freedoms as Rouhani's main focus has been boosting the sanctions-damaged economy.
Some, like 26-year-old electrician Mahmoud Karegar, said Ahmadinejad should be allowed to run.