More than 130 women have registered though none have ever been allowed to stand.
In fact, during the past Iranian year (which ended on March 20), three senior clerics who had supported President Rouhani (including Ayatollah Rafsanjani) had died, adding to the uncertainty within the overall leadership structure.
"He has no experience in foreign policy, so at least initially he will have to follow the system's grand strategy of preserving the nuclear deal and shifting any blame of undermining it to the United States", said International Crisis Group Iran analyst Ali Vaez.
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.
Analysts describe Raisi as utterly loyal to supreme leader Ayatollah Ali Khamenei, meaning he would likely remain deeply suspicious of engagement with the West but unlikely to backtrack on the nuclear deal, which had the boss's tacit consent.
Human rights issues, including the ongoing house arrest of Green Movement leaders Mir Hossein Mousavi and Mehdi Karroubi, were a significant part of Rouhani's presidential campaign in 2013, but he failed to follow through on any promises in this area.More news: Easter holiday rooted in Christian faith
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The presidency could provide a stepping stone to the top - as it was for Khamenei in the 1980s. For now, he is presenting himself as a humble servant of the poor at a time of economic stagnation. Despite the dashing number, the vetting committee, known by the Guardian Council, will only authorize a few candidates whose names are announced by the Interior Ministry within two weeks to officially run for president.
Kosar is an indigenous training jet, which has been designed, built, tested and standardized inside Iran.
"From today, protecting the nuclear deal is one of my main plans in political and economic fields", he said, alluding to U.S. President Donald Trump's dislike of the pact reached under his predecessor Barack Obama, and also to Iranian hardliners who opposed Rouhani's pursuit of detente with the West.
The situation, however, was brought into focus by the reports that the Supreme Leader - who had been in his post since 1989, after serving as President - was now terminally ill.
Ahmadinejad, who flashed a V for victory sign as he registered April 12, was embroiled in conflicts with officials during his second term and his entry is seen in apparent defiance of Khamenei, who had asked that he doesn't run to avoid polarizing the country.
A war veteran, former Revolutionary Guards commander and police chief, he is a staunch conservative.