TEHRAN, Iran (AP) -- In the end, Iran's presidential election may be defined by who doesn't vote.
As polls opened early Friday, arguments over whether to boycott the ballot still boiled over at coffee shops, kitchen tables and on social media among many liberal-leaning Iranians. 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 pro-establishment loyalist.
"There is a lot of interesting psychology going on. What is right? Which way to go?" said Salman Shaikh, director of The Brookings Doha Center in Qatar. "This is what it means to be a reformist in Iran these days."
It's 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.
Iran's presidency is a big prize, but not a crown jewel. The president does not set major policies or have the powers to make important social or political openings. That rests with the ruling theocracy and its protectors, led by the immensely powerful Revolutionary Guard
But for liberal-leaning Iranians, upsetting the leadership's apparent plans by electing Rowhani could open more room for reformist voices and mark a rare bit of table-turning after years of punishing reprisals for the 2009 protests, the worst domestic unrest in Iran since the 1979 Islamic Revolution.
"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 Tehran Mayor 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 pro-establishment figures such as hard-liner Saeed Jalili, the current nuclear negotiator. Among those blocked from the ballot was former President Akbar Hashemi Rafsanjani, who is 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 U.S. 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. In the span of 24 hours earlier this week, Rowhani received a major bump when a moderate rival withdrew to consolidate the support. Endorsements from artists, activists and others poured in.
At the final rallies, Rowhani's supporters waved his campaign's signature color purple -- a clear nod to the now-crushed Green Movement and its leader, Mir Hossein Mousavi, who has been under house arrest for more than two years. On Wednesday, the last day of campaigning, thousands of supporters welcomed Rowhani in the northeastern city of Mashhad yelling: "Long live reforms."
Some Rowhani backers also have used the campaign events to chant for the release of Mousavi and other political prisoners, including former parliament speaker Mahdi Karroubi, leading to some arrests and scuffles with police.