The 68-year-old moderate cleric, who prioritized engagement with the West and was the architect of Iran's 2015 landmark nuclear deal, registered for the May 19 poll at the interior ministry on Friday.
U.S. President Donald Trump has criticized the nuclear deal and said during his election campaign he would stop Iran's missile program. The Aradan native proceeded to register anyway, and although the Ayatollah has the final say it does not look good in terms of Mahmoud Ahmadinejad's respect for authority.
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.
A large number of conservatives appear to throw their full support behind Raisi who now holds the position of the custodian of a wealthy charity and the organization in charge of the holiest Shia shrine of Iran based in the city of Mashhad. Rouhani registered on Friday with Iran's Interior Ministry, but all candidates in Iran's election - almost 900 so far - must be approved by the Guardian Council, which is expected to announce qualified candidates on April 27.
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Britain's Prime Minister Theresa May speaks to the media outside 10 Downing Street, in central London, Britain April 18, 2017 . An early ballot will give the prime minister - or her replacement - more time to implement Brexit before another election.
First Vice President Eshagh Jahangiri, 60, also was a late entrant.
He won the past presidential elections in 2013 with a total of 18,651,668 votes.
But after his registration on Wednesday, Ahmadinejad told journalists that Khamenei's recommendation was "just advice", Iranian media reported.
Rouhani also mentioned the giant joint gas field, the North Field, Iran will be developing with Qatar.
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But it left the ailing, 67-year-old prime minister politically diminished, and the Muslim League vulnerable at the polls. Opposition leader Khan first called for an investigation into Sharif, whom his party has accused of corruption .
Incumbent President Hassan Rouhani is widely expected to seek re-election after his administration negotiated the atomic accord, though he has not filed or formally declared his candidacy. Both Mr Raisi and his father-in-law have seats on the Assembly of Experts that will choose the next supreme leader - a position for which Mr Raisi himself is often rumoured to be in the running.
Influential Shi'ite cleric Ebrahim Raisi, the custodian of a powerful organization in charge of Iran's holiest shrine, appears to be the leading hardline candidate in the presidential race, though some prominent conservatives have already thrown their weight behind Rouhani. The presidential candidates can enroll for presidential elections on April 11-16.
The former hardline president, Ahmadinejad, was a two-term president for 8 years, before President Rouhani took the office in 2013 election. Guardian Council will start vetting the candidates as of April 16.
Once the process ends on Saturday, the prospective candidates will be screened for their political and Islamic qualifications by the Guardian Council.
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House Minority Leader Nancy Pelosi and Senate Democratic Leader Charles Schumer had negative approval ratings, as did Clinton. A broad swathe of registered voters, mostly independent and Democratic voters, expressed a favorable view of him.