Even if Joe Biden triumphs at the polls, Iran’s weakened government may only have a few months to negotiate a revived nuclear deal before facing its own electoral challenge by hardliners who oppose any engagement with the west.

The narrow window has prompted calls for Biden to offer a phased approach to rejoining the Iran nuclear deal abandoned by Donald Trump in 2018, in order to show progress before the Iranian presidential election.

Iran’s reformists and centrists remain severely damaged by the failure of the original agreement to deliver economic benefits to ordinary Iranians.

Once Trump left the deal, he imposed maximum economic pressure on Tehran, blocking Iran’s oil exports, and leaving advocates of engagement with the US struggling to defend their strategy. In a recent interview in Kar Va Kargar the foreign minister Javad Zarif insisted the foreign ministry had not been naive to negotiate with the Americans, but said Trump had “blown up the entire negotiating room”.

Iran’s current president, Hassan Rouhani, was also an advocate of the deal, known as the Joint Comprehensive Plan of Action, but is standing down after two four-year terms. A range of conservatives, including members of the powerful Iranian Revolutionary Guards Corps, are preparing to stand, advocating either closer ties with China or a stronger self-reliant economic policy.

The reformist movement has not yet decided whether to put up a candidate or instead back a technocratic figure such as Ali Larijani, the former Speaker who is currently assisting Rouhani in framing a 25-year strategic partnership with China.

Reformists were trounced in spring parliamentary elections marked by a record low turn-out. The chances of persuading the disillusioned middle class to vote in the presidential election may in part depend on finding a credible candidate who can raise hopes of a resumption of talks with the west.

Biden has so far promised that “if Iran returns to strict compliance with the nuclear deal, the US would rejoin the agreement as a starting point for follow-on negotiations”.

But even if he does win, Biden would not take office until 20 January, leaving only a short time for reformists to convince Iranians that the path of engagement is worth trying again.

Some analysts say a Biden victory could be enough to change the mood in Iran – and certainly the elections are being watched with fascination in Tehran.

An article in the Sazandegi newspaper said “The most important thing that will happen in the domestic situation after the inauguration of a non-Trump president is a change in the psychological atmosphere of Iranian society and the emergence of hope for the possibility of a successful dialogue and negotiation with the US.”

On the other hand, one of Iran’s most respected analysts, Sadegh Zibakalam, suggested in the Etemad newspaper that reformists had simply lost their electoral base. He predicted a maximum turnout of 30% in the presidential election, saying “people have turned their backs on the ballot box”. Zibakalam added that disillusionment with Iran’s political process was strongest among students, the educated and urban dwellers – the very social strata that gave Rouhani his landslide victory in 2013.

Many reformists argue there is no point going through the pretence of elections since true power lies elsewhere, and it would be better to leave the conservatives visibly in charge of the executive, the clergy, the judiciary and the parliament – so they can take total responsibility for the consequences of their policy of “resistance”.

Despite the grim political mood in Iran, some western analysts say that Biden must still attempt to save the nuclear deal if he is elected.

Ellie Geranmayeh, Iran expert at the European Council on Foreign Relations, says it would be a “hard diplomatic slog”, to secure a deal. She points out that the architecture of the JCPOA currently remains in place, including the continued inspection of Iran’s nuclear sites by the UN watchdog.

Geranmeyah argues that the US with the help of the three European signatories to the deal – France Germany and Britain – should seek a sequenced deal in which there is an initial quick win, reserving more difficult issues possibly for after the Iranian presidential elections.

Her three-stage roadmap starts with an interim nuclear deal by mid February that would establish the parameters for an agreement in which Iran agrees to freeze any nuclear activities that would further exceed the deal’s limits, setting the stage for the Biden administration to lift sanctions on Iranian officials, humanitarian goods and some oil exports – as well as to start rejoining the JCPOA, a process for which no formal arrangements exists in the agreement.

By June both sides would be expected to be back in full mutual compliance with the original deal, so most US sanctions would be lifted.

This would require Iran to reduce its stockpile of low enriched uranium, dismantle advanced centrifuges at Natanz, and halt steps on research and development that go beyond the JCPOA, among other measures.

Wider talks on a broader nuclear deal would start in late 2021. A follow-on agreement supported by the European three would address nuclear sunsets in the JCPOA, Iran’s ballistic missile programme, and Iran’s policies in the Middle East.

But the barriers to such a deal are high. Mohammad Hossein Adeli, the former Iranian ambassador to the UK, has warned that “Biden must first of all regain Iran’s confidence in the negotiation process in a practical way. Iran’s trust cannot be won by words, but must be won in practice and with guarantees.”

Hassan Ahmadian, Middle East professor at Tehran university, argues that before returning to full compliance, Iran will demand compensation for the economic harm suffered at the hands of Washington’s sanctions, as well as remedying outstanding shortcomings in the JCPOA.

Iran feels the 2015 deal obliged it to curb its civilian nuclear programme before the west was required to take any steps, whilethe deal failed to penalise the US for violating its terms. “Simply returning to full compliance based on the US rejoining the deal is no longer feasible. The trust deficit has skyrocketed to the extent that a change of faces in the Oval Office will not alter this fact,” he argues.