A potential spoiler appeared on Wednesday, when former hardline president Mahmoud Ahmadinejad made the shock move of registering for the election against Khamenei s advice. More than 1,010 people have signed up so far for the vote.
However, Ahmadinejad said Wednesday that the Supreme Leader never barred him from rerunning for the presidency.
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 worldwide community.
Rouhani's defended the policy of 'strengthening the defensive prowess of Iran's Armed Forces'.
The nuclear deal was engineered by the Rouhani administration and went into effect in 2016.
The election on May 19 is seen by many as a referendum on the nuclear agreement and its ability to improve the country's sanctions-burdened economy.
Raisi, a former Tehran deputy prosecutor, is Chairman of the Astan Quds Razavi charitable foundation and a close ally of Iran's supreme leader Ayatollah Ali Khamenei. That's not to say it will be easy for Rouhani.
Nevertheless, the aggregate opposition to Rouhani's candidacy is so serious that some hardliners have even put forth the idea of having his candidacy disqualified by the Guardian Council, which will vet all prospective candidates by April 27 for their perceived loyalty to the theocratic regime and the principles of the Islamic Republic.
Ahmadinejad said the strike on Syria could have happened even if Hillary Clinton had won the USA election. He is also a member of Assembly of Experts, an all-cleric body that will rule on the successor for the Supreme Leader. The supreme leader also serves as the country's commander in chief over its military and the powerful Revolutionary Guard, a paramilitary force involved in the wars in Iraq and Syria that also has vast economic holdings across Iran.
U.S. Secretary of State John Kerry (L), U.S. Secretary of Energy Ernest Moniz (2nd L), Head of the Iranian Atomic Energy Organisation Ali Akbar Salehi (2nd R) and Iranian Foreign Minister Javad Zarif (R) wait with others ahead of a meeting at the Beau Rivage Palace Hotel in Lausanne on March 26, 2015.
Within Iran's complex mix of clerical rulers and elected officials, Khamenei has the final say on all state matters. "I think the fact that Raisi is coming, unless he steps aside, it looks very unlikely to me that the nezam [ruling system] would allow Raisi to be humiliated in an election".
"Those who sympathise with the heads of sedition must know that the great nation of Iran will never forgive this great injustice". Security forces answering only to the supreme leader also routinely arrest dual nationals and foreigners, using them as pawns in global negotiations.