Mohammad Khatami, the outgoing president of Iran, stepped down on 2 August 2005, after serving his maximum two consecutive four-year terms according to the Islamic republic's constitution.

Factors thought to have contributed to Ahmadinejad's victory include mobilization of mosque networks and conservative/hardline voters, and a protest vote against corrupt elite insiders and for "new political blood".

But the most unpredictable was the disqualification of conservative Reza Zavare'i, a former member of the Guardian Council and an approved presidential candidate for two previous elections.

Also, there was a high probability of rejection of women, because of an ambiguous term ("rejāl", رجال) in the Constitution of Iran, a requirement for presidential candidates, which may be interpreted as either "men" or "nobles".

Mohsen Rezaee, one of the approved conservative candidates, who is the Secretary of Expediency Discernment Council and a previous commander of the Iran–Iraq War, withdrew in the evening of 15 June.

Where in 2002 he had said that exposing a single strand of a woman's hair from behind hejab was "a dagger drawn toward the heart of Islam," in 2005 he described his red line as "no nudity," in a campaign meeting with Iranian youth.

After the first round of the election, some people, including Mehdi Karroubi, the pragmatic reformist candidate who ranked third in the first round but was the first when partial results were first published, have alleged that a network of mosques, the Islamic Revolutionary Guard Corps military forces, and Basij militia forces have been illegally used to generate and mobilize support for Ahmadinejad.

As a reply, Karroubi resigned from all his political posts, including an Advisor to the Supreme Leader and a member of Expediency Discernment Council, on both of which he had been installed by Khamenei.

The day after, on 20 June, a few reformist morning newspapers, Eghbal, Hayat-e No, Aftab-e Yazd, and Etemaad were stopped from distribution by the general prosecutor of Tehran, Saeed Mortazavi, for publishing Karroubi's letter.

Akbar Rafsanjanī, the leading candidate, has also pointed to organized and unjust interventions by "guiding" the votes, and has supported Karroubi's complaint.

Some of the controversies involve activities of the Guardian Council such as the publishing an opinion poll before the election giving Ahmadinejad front-runner status.

The Islamic Republic government of Iran, especially the Supreme Leader and the higher offices, publicly considers the turnout of the voters, which was about 64% in the first round, to resemble the support of the population for the regime, while some voters consider voting for the candidates less aligned with the supreme leader as a vote against the current practices of the regime.

[19] The first round of the election was a very close race with minor differences in the number of votes won by each candidate which led to a run-off a week later with Ahmadinejad and ex-president Akbar Hashemi Rafsanjani participating.

There were seven people running for the post out of more than a thousand initial candidates, most of whom were disqualified by the Guardian Council, which is responsible for vetting by constitution for election.

Rafsanjani, who had been regarded as the front-runner and had positioned himself as a centrist, was defeated by Ahmadinejad in the run-off, while reformist candidate Mostafa Moeen fared poorly and finished only fifth in the first round.

But after the results for the run-off were made public, the comparison was considered void due to the loss of the moderate candidate Rafsanjani, although Ahmadinejad's opponents formed an alliance against him.