When she voted for the reformist candidate in Iran’s last presidential election, Fatemah, a retired schoolteacher in Tehran, said she did so with a “slight hope for change.” This time, she holds no such illusions about the election being held Friday — and like many other people, has no plans to cast a ballot.

“I will not vote in the Islamic regime ever again,” she said in a text message, citing deep disappointment with the performance of the government but also disgust with the current field of candidates, which is dominated by conservatives and hard-liners. Everyone she knew had decided to boycott the election, she said.

Recent polls in Iran have forecast historically low voter turnout in the contest to succeed President Hassan Rouhani, a moderate, as Iranians exhausted by years of political turmoil and economic hardship turn their backs on Iran’s politicians. A display of voter apathy is almost certain to benefit Ebrahim Raisi, an ultraconservative cleric who is the preferred choice of the hard-line establishment and the overwhelming favorite to win in several polls.

Raisi, who unsuccessfully ran for president four years ago, is a loyalist of Ayatollah Ali Khamenei, Iran’s supreme leader, and viewed as his possible successor. A chameleon-like figure who has avoided taking strong positions on issues during the recent campaign, Raisi has been linked by human rights groups to mass killings of dissidents in 1988, when he served on a panel involved in sentencing prisoners to death.

He has taken a dim view of negotiations with the United States, calling such talks contrary to Iran’s “values,” while at the same time signaling a willingness to revive the nuclear deal between Tehran and global powers, a critical step in removing crippling Western sanctions on Iran.

His likely victory — which would place all the levers of power in Iran in the hands of hard-line factions — has set off an urgent debate in recent days among reformists about whether to participate in the election and support a more moderate candidate or to boycott the vote.

Ali, a 55-year old electrician in Tehran, said he was torn. On the one hand, “it is better if Raisi wins so the hard-liners will have no excuses for the failures and mismanagement of the country, and they will be fully accountable,” he said.

But there was also a “high chance that Raisi’s presidency will mean even darker ages for the future of Iran,” he said. Ali, like others interviewed for this article, spoke on the condition that he be identified by his first name to avoid retribution by the authorities.

Raisi, who most recently served as head of Iran’s judiciary, was among seven men approved last month to run in the election by the 12-member Guardian Council, a body that vets candidates for elected office and whose decisions reflect the preferences of the supreme leader.

The council’s selections drew a torrent of criticism for disqualifying several prominent figures associated with centrist or reformist factions, including Ali Larijani, a former parliament speaker and nuclear negotiator, and Eshaq Jahangiri, a reformist and Rouhani’s vice president.

The choices were seen by analysts as an unusually brazen effort by the conservative establishment to shape the outcome of the election — and a risky move for a leadership that has touted high voter turnout as evidence of the Islamic Republic’s legitimacy. On Wednesday, two prominent hard-line candidates dropped out of the race, further clearing the way for a Raisi victory and deepening a conviction among many reform-minded voters that the contest was rigged. (If no candidate wins at least 50 percent of the vote, the election would go to a runoff.)

After a reformist candidate also dropped out Wednesday, Abdolnaser Hemmati, who served more than two years as governor of Iran’s Central Bank, remained as the only nonconservative candidate in the race and Raisi’s only real challenger. On Wednesday, during an online discussion on Clubhouse hosted by a prominent reformist political figure and attended by thousands of people, Hemmati urged people not to cede more political ground to Iran’s hard-liners.

“I am alone against these [people] if you don’t support me with your votes,” he said. “I ask the boycotters, how do you think not voting can help the country? Why should we surrender all the power in our country to one camp?”

The host of the discussion, Behzad Nabavi, said that hard-liners would prefer lower turnout and that those who boycott were “cooperating” to guarantee a landslide conservative victory. One participant in the discussion, though, asked how voting would make a difference, given the Rouhani government’s failure to produce meaningful change.

“What can Mr. Hemmati do that Mr. Rouhani couldn’t? Isn’t it true that the president does not even have the authority to choose his own deputy?” the participant asked. For instance, Hemmati “promises that he can free the Internet in Iran,” the man said, noting that Rouhani had been unable to prevent the censorship or filtering of websites and Internet apps such as Telegram.

The question of participation in the election has split Iran’s reformist circles. A statement attributed to Mohammad Khatami, a pro-reform cleric who served two terms as Iran’s president, appeared to encourage people to vote, warning of a “minority” that “imposes its will on society at any cost.”

But a recent statement by Mir Hossein Mousavi, an opposition leader who is under house arrest, showed sympathy for the boycotters. “I will stand by those who are fed up with the humiliating and engineered elections — those who are not willing to give in to behind-the-scenes decisions for the future of the country,” he said this week.

The most recent polling data from the Iranian Student Polling Agency predicted voter turnout at 42 percent, far lower than in previous presidential contests. Iran’s political establishment responded with an urgent call for people to get out and vote.

In a televised speech Wednesday, Khamenei blamed Iran’s enemies and foreign media for suppressing the vote, “in order to not allow the glory of elections to be put on display.” He said, “God willing, the people will participate, and this will give more prestige to the Islamic Republic,” he said.

Rouhani, in a speech encouraging people to vote Thursday, said that while there were “grievances” about how the election was being conducted, “the inadequate work of a group or an institution should not prevent us from a very great national and legal duty,” in an apparent reference to the Guardian Council.

Nima, a 30-year-old artist in Tehran, had weighed all the conflicting opinions and decided it was the “right act to vote,” he said in a text message. The election was critical, coming at a time when the question of who would succeed the aging supreme leader was coming to the fore.

“If we do not do all we can to stop the regime from having entirely unrivaled power, any kind of resistance or activism to make changes in the future will be much harder,” he said.