As with the first time he ran, in 2013, Rouhani, a "moderate", is battling "hardline conservatives", Judge Ebrahim Raisi (protegee of the Supreme Leader), and military heavyweight Mohammad Bagher Qalibaf, the current mayor of Tehran.
They have also been called "Principalists" (the label they prefer), and, often in the West, "religious extremists" - Rouhani used the term in his first campaign in reference to his predecessor, Mahmoud Ahmadinejad.
Today, another label has slipped in quietly to describe Rouhani's rivals: Populists. However, unlike in the West, where populism has been used in relation to US President Donald Trump, French presidential candidate Marine Le Pen or Italian Beppe Grillo, in Iran the populists aren't overturning the establishment; they are the establishment. It's Rouhani, the reformist, the liberal internationalist, who represents the opposition.
Looking at the Iranian election through a populist lens makes the murky politics of the Islamic Republic more transparent, particularly in light of the populist moves so recently chronicled in the US and Europe. It also gives a clue as to what populist-led countries look like in the long term, as well what they're like for both allies and enemies on the outside.
Iran's establishment has a quiver-full of populist practices it has honed over the years. Three in particular stand out - not least because they have been recently on display on several Western stages:
'Making Iran Great Again'
The economy, according to opinion polls, is the issue of greatest popular concern, with 72 percent of Iranians indicating they don't feel it has improved, or improved sufficiently, since the passage of the Joint Comprehensive Plan of Action (JCPOA, the nuclear agreement).
Despite Rouhani's record of raising GDP growth to 7 percent, and rescuing the economy from falling into hyperinflation as a result of Ahmadinejad's ill-managed statist policies (today, according to the IMF, inflation is around 9.2 percent), Qalibaf and Raisi accuse him of failing to deliver the promised rewards of sanctions relief.
Their reason: Rouhani has become too chummy with the West, and is threatening Iran's economic well-being through global financial and trade deals.
Their solution: to follow Supreme Leader Khamenei's idea of a "resistance economy" which prioritises domestic production and self reliance, the only way to "fight unemployment and recession, control inflation and confront the threats of enemies", as he explained in a speech last year. Qalibaf promises to create five million jobs and double the country's income during his tenure; Raisi is offering 1.5 million more jobs a year, and says that he will triple handouts to the poor. Rouhani's team have hit back by calling this populist rhetoric empty promises, noting that creating so many jobs would need economic growth of 26 percent - a pipe dream.
Yet, although the same populist practices were tried - and failed - under Ahmadinejad, appealing to those "left behind" with promises of payouts, a jobs miracle, and utopian well-being are all populist mainstays in the Islamic Republic, made all the more legitimate as their proponents see the same rhetoric now copied elsewhere - in Trump's promises to back out of global trade deals that hurt "regular Americans", and Theresa May's assurances that Britain's divorce from the EU will boost British sovereignty and strengthen the UK economy.
Rouhani, who put Iran's economy back on track after the ravages of sanctions-enforced financial and trade isolation, sees such policies as the route to arrested development.
Although touted at the time as a "win-win", the nuclear deal with its accompanying sanctions relief has lost its lustre in Iran. Rouhani's rivals accuse him of signing away Iran's sovereign rights and appeasing the West. It is time, say both Raisi and Qalibaf, to stop compromising and to start pursuing a foreign policy that protects Iran's interests and prestige. Neither has officially rejected the JCPOA, but they condemn Rouhani for succumbing to US and European duplicity. International banks, they point out, still fear US fines if they offer Iran financing, the US Congress is plotting further sanctions in response to Iran's missile tests - even though they're not precluded by the JCPOA, and Trump's administration is cozying up to Iran's biggest rival, Saudi Arabia, as Washington has put "Iran on notice" while it reviews US policy towards Tehran.
Every time Iran extends its hand, these establishment candidates point out, the US has returned with an iron fist, and now again, Trump's administration has signalled that it's not committed to the nuclear agreement.
What distinguishes the populist establishment in Iran from the conservative populist experiments in the US, Italy or Britain, is that fiction is now a plank of the platform.
Rouhani's response is that Iran's foreign policy should serve its domestic economy - a campaign slogan he used to good effect in his first presidential run, and which he is drawing on to argue that the bigger fruits of sanctions relief will come during a second term under the same consistent liberal leadership. Indeed, Rouhani's view is that Iran's own unpredictability and self-serving foreign policies, not just Western distrust and antagonism, have isolated and hurt it over the years.
For Rouhani, the populist idealism of Iran against the rest has repeatedly proven unserviceable in a globalised world. Only when a country has been led by liberals and reformers has it made progress and accrued credibility and prosperity.
'Controlling the Media'
When the phrase "alternative facts" or "false facts" crashed onto the American conscience, Iranians and other Middle Easterners interviewed for this story expressed amazement at Western idealism. "We're used to false facts - our governments always use them," said a journalist.
Although Iran tops the charts for blog building and mobile calling, the tussle between the establishment and opposition reformists over media control has often been brutal, and has swung widely from one administration to another. Internet activism helped Rouhani to win his first election, and he has refused to succumb to pressure from his critics, including the Islamic Republican Guard's Chief of Intelligence, to block social media - particularly the highly popular Telegram app. Among his first statements on the campaign trail was that a vote for him was a vote for freedom of expression.
Concerned that the media might be a key in sowing discord among a deeply divided population (conservative vs modernist), Supreme Leader Khamenei is keen to project an image of strong and stable leadership. His Islamist vision marries revolutionary idealism with religion and state, a polemic that, like most populism, does not allow multiple interpretations. To inspire the nationalistic fervour to make "Iran Great Again" and view the world from the lens of "Iran First", a media that exudes patriotism, revolutionary activism, and broad buy-in is critical - even if it's not all drawn from truth.
What distinguishes the populist establishment in Iran from the conservative populist experiments in the US, Italy or Britain, is that fiction is now a plank of the platform. To believers, it furnishes credibility; to domestic opponents and international players, it introduces a strange air of discordant unreality. For Rouhani, it is anathema to good governance. To US Defence Secretary Jim Mattis, who sees Iran as "not a nation state … but a revolutionary cause devoted to mayhem", it is rhetoric in the service of the nation.
Roxane Farmanfarmaian is a lecturer at the University of Cambridge, Centre for the Study of the International Relations of the Middle East and North Africa.
The views expressed in this article are the author's own and do not necessarily reflect Al Jazeera's editorial policy.