Iran’s ruling theocracy was unable to overcome its notorious infighting and unite behind a single candidate in Friday’s presidential election, which has suddenly boosted the prospects of the lone moderate in the race and rekindled interest among some who had planned to boycott.

A cleric and former nuclear negotiator with only modest reform credentials, Hassan Rowhani stirred little enthusiasm when he announced his candidacy in April. Even when he was one of only two centrists to survive the vetting of the conservative, cleric-controlled Guardian Council, he was given little chance of drawing more than a sliver of the vote.

But with the withdrawal earlier this week of Mohammad Reza Aref, the only other candidate not thoroughly beholden to the religious hierarchy under supreme leader Ayatollah Ali Khamenei, Rowhani is now seen as having a shot at emerging high enough in the six-candidate field to advance to a June 21 runoff.

Aref, a Stanford-educated academic who was vice president under former President Mohammad Khatami, dropped his presidential bid at Khatami’s urging to strengthen Rowhani's chances and give voters tired of Iran’s ravaged economy and international isolation a viable alternative to the status quo.

The Guardian Council scratched more than 600 would-be candidates last month, including former president and reformist Ali Akbar Hashemi Rafsanjani and incumbent President Mahmoud Ahmadinejad’s preferred successor, Esfandiar Rahim Mashaei.

The barring of Rafsanjani, a revered patriarch of the 1979 Islamic Revolution, was seen by Iran analysts as a reflection of Khamenei's fear that the popular ex-president, if returned to the executive office, would seek to shift authority from the religious clique to elected officials.

Rafsanjani's exclusion on obvious political grounds reinforced liberal and reform-minded voters’ impressions that the electoral system is corrupted by the ruling clerics and vulnerable to fresh manipulation.

After the last presidential election in 2009, tens of thousands of angry voters took to the streets for months to claim fraud was behind the declaration of Ahmadinejad as the winner. The protests, the largest since the 1979 revolution, drew a harsh police crackdown that continues with the house arrest of reformist candidates Mir-Hossein Mousavi and Mehdi Karroubi.

But those who follow Iran’s inscrutable backroom politicking through professional contacts and conversations with relatives say Khamenei’s blatant efforts to ensure the theocracy’s continuing grip on the main levers of power has failed because the clerics couldn’t agree on which conservative to rally behind. And the prospect of the five  loyalists splintering the vote has given rise to expectations among disillusioned reform advocates that Rowhani, while far from what could be considered an opposition figure, might make it into the second round if enough would-be boycotters decide to turn out.

“I urge them to vote,” Rafsanjani, whose opinion is widely respected among the young and the liberal, was quoted as saying by several pro-reform media outlets Thursday.

Polls cited in state-run media and reported by Western news agencies suggested for the first time in the closing hours of the campaign that Rowhani would get about 15% of the vote. A survey by the Mehr Center for Opinion Polling projected Tehran Mayor  Mohammed Baqer Qalibaf would garner about 18% and chief nuclear negotiator Saeed Jalili about 10%. A survey cited by the Fars News Agency two days earlier said Rowhani would come in third behind Qalibaf and Jalili.

Analysts note that the opportunity to derail the carefully orchestrated election could be as much of a lure for reformists to abandon their intended boycott as is the prospect of a moderate winning or at least making it into the runoff.

“The whole purpose of having Aref drop out and having Rowhani become the favorite son of the reform camp was deliberately and unquestionably intended to get people to come out and vote,” said Gary Sick, a senior research scholar at Columbia University and a former National Security Council member under presidents Ford, Carter and Reagan.

“What has happened in virtually every election is that, when given the least opportunity, the people of Iran vote against the regime,” said Sick, who was chief White House aide for Iran during the revolution and hostage crisis. “It is not at all inconceivable that the reformist camp, if enough people decide to vote, could come through this election in good shape.”

Alireza Jafarzadeh, a veteran Iranian affairs analyst and member of the National Council of Resistance of Iran, a parliament-in-exile, has low expectations of Rowhani taking any positions different from those of Khamenei. But he sees weakness and discord behind the ruling clerics'  failure to compel the five conservative candidates to decide who among them had the best chances and unite behind him.

“The reason Rafsanjani was disqualified was because he would really have heightened the infighting within the regime and raised it to a new level. He would have insisted on sharing power with Khamenei,”  Jafarzadeh said.

That Rowhani won the Guardian Council’s approval to run for the presidency shows that the ruling clerics see him as like-minded, and as a cleric he can be expected to protect the religious hierarchy's interests, Jafarzadeh said. He added that in the unlikely event that the 65-year-old Rowhani triumphs, he would make few if any changes to the limited aspects of the president’s control.

“The big news is the fact that the regime is now struggling with this election,”  Jafarzadeh said. “Despite all of the disqualifications of those they didn’t like, they still have a major problem. They are still paranoid about a recurrence of the 2009 uprising because that potential hasn’t evaporated. It has only condensed.”

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A foreign correspondent for 25 years, Carol J. Williams traveled to and reported from more than 80 countries in Europe, Asia, the Middle East and Latin America.