But conservatives have targeted Mr. Rouhani for what they regard as his softness toward the United States and tolerance of Western culture. They also have sharply criticized him for what they call his misleading prediction that the nuclear agreement would herald an economic boom in Iran, where joblessness remains pervasive and the economy is the most pressing campaign issue. Still, Mr. Rouhani is considered the front-runner.
Ebrahim Raisi, 56
Widely believed to have the backing of Iran’s supreme leader, Ayatollah Ali Khamenei, Mr. Raisi is known as a hard-line cleric who has spent most of his political career as a prosecutor and judicial official, starting at age 20, two years after the revolution. Last year he was appointed by Mr. Khamenei as the custodian of Astan Quds Razavi, a well-endowed Islamic charity in charge of Imam Reza Shrine, one of the holiest sites in the Shia branch of Islam that prevails in Iran.
Mr. Raisi also is a member of the Assembly of Experts, the clerical body that supervises the work of the supreme leader, and is regarded as a possible successor to Mr. Khamenei. Mr. Raisi wears a black turban identifying him as a descendant of the Prophet Muhammad.
Critics contend that Mr. Raisi, with his strict anti-Western views, would lead Iran back into isolation like President Rouhani’s unpopular predecessor, Mahmoud Ahmadinejad. Rights advocates say he was among the judicial authorities responsible for mass executions of leftists and dissidents during political turmoil in 1988, when roughly 4,500 people were believed to have been killed. Mr. Raisi is not known to have spoken in the campaign about that era.
Eshaq Jahangiri, 60
Mr. Rouhani’s vice president, Mr. Jahangiri is a reformist who joined the race in a politically strategic move to help Mr. Rouhani counter their conservative critics and defend the nuclear accord, which many Iranians regard as an exemplary achievement even if it has yet to yield major economic benefits. He is widely expected to drop out and endorse Mr. Rouhani. “Our government has started along a good path — the nuclear issue was settled, we have stabilized the economy, hope has returned,” Mr. Jahangiri said in a recent interview with Agence France-Presse. “I am confident Iranians will vote for this government to continue its work.”
Mohammad Baqer Qalibaf, 55
Like Mr. Ahmadinejad, Mr. Qalibaf established his political trajectory as Tehran’s mayor. A onetime airline pilot who still has his flying license, he boasts of his hard-line credentials as a former Revolutionary Guard commander and police chief, and has resisted calls by other conservatives to step aside and endorse Mr. Raisi.
Mr. Qalibaf has assailed President Rouhani over a failure to create jobs and has predicted that “an unemployment tsunami will wash away the government.” Rights advocates have accused him of having bragged about crushing protests and beating demonstrators during his police career. Mr. Qalibaf also has faced criticism over the collapse of a prominent high-rise building in Tehran last January that killed at least 20 firefighters.
Mostafa Agha Mirsalim, 69
An engineer and former minister of culture and Islamic guidance, Mr. Mirsalim was an adviser to Ayatollah Khamenei when he was president in the 1980s. He is considered a pious hard-liner known for closing reformist newspapers and denouncing what he considers a Western cultural onslaught subverting Iran’s youth.
Mostafa Hashemi-Taba, 70
A former top official of Iran’s physical education organization and National Olympic Committee, Mr. Hashemi-Taba is closely associated with Mohammad Khatami, the former reformist president who preceded Mr. Ahmadinejad. He has been a strong defender of the nuclear accord and may drop out to support Mr. Rouhani.
Mr. Hashemi-Taba has been outspoken in his ridicule of hard-line conservatives over what he calls their denial of the destructive effects of nuclear sanctions during Mr. Ahmadinejad’s tenure.
“These were the ones who buried their heads in the sand and said sanctions had no impact,” he said. “They emptied the Treasury.”