A moderate, mid-ranking cleric, Rafsanjani currently heads the powerful Expediency Council, which mediates in disputes between parliament and the Guardians Council, an unelected religious watchdog committee. He is also deputy chairman of the Assembly of Experts, the body that elects Iran's supreme leader.
On 17 June, hard-line Tehran Mayor Mahmud Ahmadinejad placed a surprisingly close second in the first round of presidential voting. Since then, Rafsanjani and his supporters have been portraying his candidacy as the one to save Iran from the danger of fanaticism and rule by military force.
Mehdi Karrubi, the moderate cleric who finished third in the first round, is calling on his supporters to vote for Rafsanjani on 24 June. "Otherwise," he said, "they are going to make an Iranian Taliban here."
On 21 June, the 70-year-old Rafsanjani promised a gathering of students that, if elected, he will champion reforms. He also spoke in favor of freedom of expression, within Iranian laws. "If the media, news presenters, writers, and students act within the framework of the law, I see it as the duty of the government -- any government -- to recognize their right [to free speech] and not to suppress their views," he said.
Rafsanjani's two-term presidency, from 1989 to 1997, brought some modest social and economic reforms. He is also credited with spurring Iran's reconstruction following the 1980-88 war with Iraq.
Farhang Naderi is the speaker of the student committee at Rafsanjani's election headquarters. He told Radio Farda that Rafsanjani was a prime mover in instituting reforms. "During [Rafsanjani's] eight-year [presidency], all of Iran's economic infrastructures were amended, and those economic reforms led to the creation of a reformist government, such as [that of outgoing President Mohammad] Khatami," Naderi said.
Naderi believes Rafsanjani would be effective in confronting Iran's conservative camp with reform plans.
But some observers are skeptical that Rafsanjani can bring about real democratic changes in Iranian society. Others note that Rafsanjani has been accused of involvement in the killing of dissidents inside and outside Iran.
Abdolkarim Lajidji, president of the Paris-based League for the Defense of Human Rights in Iran, says Rafsanjani does not have a record of support for human rights.
"During the term of Iran's previous parliament, the government sent two bills to the parliament -- one for Iran to join the [UN] Convention Against Torture, and the other was for Iran to join the [UN] Convention on the Elimination of All Forms of Discrimination Against Women," Lajidi said. "The parliament adopted them, but both bills were rejected by the Guardians Council as un-Islamic. Both bills were sent to the Expediency Council under the leadership of Mr. Rafsanjani. If Mr. Rafsanjani claims he is really in favor of reforms, why didn't he adopt those bills?"
Rafsanjani and his supporters have not responded to such criticism.
Emadeddin Baghi is a prominent journalist and rights activist in Iran. He says Rafsanjani's defeat tomorrow would lead to a worsening of the human rights situation in the country.
Rafsanjani has spoken against interference in people's private lives and has said more attention needs to be paid to the concerns of Iran's youth. He has also said that, if elected, he would address Iran's high unemployment and work hard to resolve the country's nuclear standoff with the West. He says he has enough influence to mend ties with the United States, which has labeled Tehran part of an axis of evil. But first, he says, the United States should end what he calls its hostile policies toward Iran.
"What I have said is that if the United States would like to improve its relations with Iran, it should take the first step," Rafsanjani said.
Rafsanjani was born in 1934 to a family of pistachio farmers. He studied theology at a seminary in the city of Qom. There are many stories about Rafsanjani being a man of great wealth, but he has always denied them.
Outgoing President Khatami this week gave his implicit backing to Rafsanjani's candidacy, saying political power should go to those who believe in defending freedom and not those who endanger democracy.
(Radio Farda correspondent Siavosh Ardalan contributed to this report.)
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For RFE/RL's full coverage of Iran's elections, see "Iran Votes 2005"