Result may affect range of issues from future of 2015 nuclear agreement to fate of dual-national prisoners held in Iran.
Iranians head to the polls on Friday to elect a successor to President Hassan Rouhani, the reformist leader whose second term in office is coming to a close.
Rouhani was one of the key architects of the 2015 nuclear deal which saw Iran consent to limiting its nuclear programme in exchange for sanctions relief.
The vote comes at a moment of tension over the accord.
Then-President Donald Trump unilaterally withdrew the United States from the deal in May 2018 and reimposed sanctions on Tehran.
Iran responded by steadily lowering its compliance with the agreement, of which it remains a signatory.
The other current signatories are the United Kingdom, France, Germany, the European Union, Russia and China.
The European parties to the deal, which is officially known as the Joint Comprehensive Plan of Action (JCPOA), have scrambled to restore it since Washington’s withdrawal.
They have sought to mitigate the effect of the reapplied sanctions on Tehran, but with limited success.
However, hopes of saving the JCPOA have risen recently on the back of US President Joe Biden’s elevation to the White House.
Biden wants to resurrect the deal and even extend its terms, and several rounds of indirect US-Iranian negotiations have taken place.
The talks are not direct because Iran refuses face-to-face meetings, but the US has held discussions with many of the participants.
Now, all eyes are on Iran.
Will the outcome of Friday’s poll affect the future of the pact?
Here’s what you should know:
Although internal differences remain, it appears different political factions in Iran have come to a shared understanding that restoring the nuclear accord is necessary for lifting the harsh sanctions that have affected every aspect of the country’s economy.
Conservative candidate Ebrahim Raisi, widely seen as the frontrunner, said during a recent televised election debate that he would honour the nuclear deal, adding he that plans to form a “strong” government to steer it in the right direction.
Supreme Leader Ali Hosseini Khamenei, Iran’s chief decision-maker on foreign and nuclear policy, has said Tehran will return to the accord once the US shows it will abide by its commitments under the deal.
Iran has said it wants “all” of the 1,500 or so sanctions imposed, reimposed or relabelled during the Trump era removed, after which it will spend an unspecified time verifying that they have been lifted in action.
It also wants a guarantee that the US will not unilaterally leave the deal in the future, although it is not clear what form that guarantee will take.
The Islamic republic has expressed willingness to return to its own commitments under the JCPOA, but has not publicly announced how that could be done or exactly how long it would take, and is against expanding the initial agreement.
Earlier this week, Iran’s top negotiator, deputy foreign minister Abbas Araghchi, said the country wants a “good” agreement that will serve its interests and one that is not rushed.
He has previously warned that Iran will pull out of the talks immediately if it considers other sides are not serious about the discussions.
All six candidates running for the presidency, one of whom is a moderate, have backed the continuation of negotiations aimed at reviving the pact.
The outcome is therefore not expected to change Tehran’s current stance – trying to resuscitate the deal.
Crucially, so has Khamenei, who has ultimate authority over Tehran’s stance on the issue.
“Sanctions relief is something that the [Iranian] system as a whole is seeking,” Sanam Vakil, a deputy director and senior research fellow for the UK-based think-tank Chatham House’s Middle East and North Africa programme, told Al Jazeera.
“So I don’t see the process being impacted [by the Iranian election] unless the US refuses to compromise on sanctions relief,” she said.
Under Biden, the US has expressed an interest in restoring the JCPOA.
His administration sees the revival of the agreement as a stepping stone towards a wider deal – one that places tougher limits on Iran’s nuclear programme and covers missile testing as well as several other issues. For its part, Iran has stated it does not want to expand the deal.
The other signatories to the pact are keen to bring the US back to the accord and ensure Iranian compliance with its terms.
European powers have repeatedly pushed their ally, Washington, to return to the deal.
Meanwhile, Chinese President Xi Jinping has made clear he supports Iran’s “reasonable demands” regarding the future of the agreement, while Russian President Vladimir Putin has said Moscow, an ally of Iran, hopes for a full restoration of the accord under its initial terms.
Russian and Chinese envoys have joined representatives from the UK, France, Germany, the EU and Iran itself for the talks aimed at saving the deal.