TEHRAN — In the end, Iran’s presidential election may be defined by who does not vote.
Arguments over whether to boycott Friday’s ballot still boiled over at coffee shops, kitchen tables, and on social media sites among many liberal-leaning Iranians on the eve of the voting. The choice — once easy for many who turned their back in anger after years of crackdowns — has been suddenly complicated by an unexpected chance to perhaps wage a bit of payback against Iran’s rulers.
The rising fortunes of the lone relative moderate left in the race, former nuclear negotiator Hasan Rowhani, has brought something of a zig-or-zag dilemma for many Iranians who faced down security forces four years ago: Stay away from the polls in a silent protest or jump back into the mix in a system they claim has been disgraced by vote rigging.
Which way the scales tip could set the direction of the election and the fate for Rowhani, a cleric who is many degrees of mildness removed from being an opposition leader. But he is still the only fallback option for moderates in an election that once seemed preordained for a proestablishment loyalist.
‘‘There is a lot of interesting psychology going on,’’ said Salman Shaikh, director of the Brookings Doha Center in Qatar. “What is right? Which way to go? This is what it means to be a reformist in Iran these days.’’
It is also partly a political stock-taking that ties together nearly all the significant themes of the election: the powers of the ruling clerics to limit the choices, the anger over years of pressures to muzzle dissent, and the unwavering claims that the last election was stolen in favor of Mahmoud Ahmadinejad, who cannot run for a third consecutive term.
‘‘Rowhani raises a lot of interesting questions,’’ said Scott Lucas, an Iranian affairs expert at Britain’s Birmingham University. ‘‘Among them, of course, is whether he gets Iranians who have rejected the system to then validate the system by voting again.’’
And there are many other factors at play.
Many Iranians say they are putting ideology aside and want someone who can stabilize the sanctions-battered economy — one of the roles that does fall within the presidential portfolio. This could boost candidates such as the mayor of Tehran, Mohammad Bagher Qalibaf, who is seen as a fiscal steady hand.
Also, the rest of the candidates approved to run by election overseers — from more than 680 hopefuls — are stacked heavily with proestablishment figures such as hard-liner Saeed Jalili, the current nuclear negotiator. Among those blocked from the ballot was former president Akbar Hashemi Rafsanjani, one of the patriarchs of the Islamic Revolution.
The vetting appeared aimed at bringing in a pliant and predictable president after disruptive internal feuds with Ahmadinejad, who upended Iran’s political order by trying to challenge the authority of Supreme Leader Ayatollah Ali Khamenei. The desire for calm is also fueled by the critical months ahead, which could see the resumption of nuclear talks with the United States and other world powers.
But the presumed plans have met an obstacle in the form of Rowhani, who is a close ally of Rafsanjani and is now backed by other reformist leaders who had previously seemed resigned to defeat.