BEHROUZ MEHRI/AFP/Getty Images

Khomeini's ghost: Is this former prime minister and student of the Iranian Revolution really the reformer his supporters hope?

"Death to potatoes!"

This pointed exclamation, hurled from the crowd at a recent rally for Iranian presidential candidate Mir Hossein Mousavi, might seem an odd way to show support for a man who has twice been Iran's prime minister and is today incumbent Mahmoud Ahmadinejad's most formidable opponent. But potatoes, it seems, have everything to do with the Iranian elections this year. Ramping up the public distribution of potatoes, along with a wide range of other government subsidies and alms, has become Ahmadinejad's preferred strategy for buying votes. While the Western world has focused on the incumbent's inflammatory statements about the Holocaust and his confrontationist nuclear policy, his domestic critics have focused their ire on his flawed economic remedies and populist demagogy, in addition to his erratic diplomatic style. Hence, potatoes, and the surprise return of Mousavi, a man little known outside Iran.

Although many Iranian liberals - and a few Western analysts - see in Mousavi a potential reformist corrective to Ahmadinejad's excesses, the former prime minister, should he overcome long odds and win in June, is likely to tweak, rather than overhaul, the Islamic Republic. Think Leonid Brezhnev, not Mikhail Gorbachev.

The 67-year-old* Mousavi has never run for elected office, having been appointed prime minister at the age of 40 after serving briefly as foreign minister and editor of the conservative Islamic Republican Party's newspaper. He is not especially charismatic, and appears to lack the kind of solid organizational machinery that makes Ahmadinejad, with his religious conservative base, the reigning favorite. Mousavi, moreover, has spent the past two decades largely out of the public eye, pursuing his life-long interests in architecture and painting. For some two thirds of Iran's extremely young population, his legacy as prime minister has little or no resonance today.

Yet Mousavi, the son of an Azeri tea merchant, is nonetheless an ambitious and skilled politician, keen to surround himself with similarly able characters. He helped steer Iran through a good part of the tumultuous 1980s -- during a bloody war with Iraq and multiple episodes of internal unrest. To meet the formidable challenges, Mousavi convened two ambitious cabinets from across the political spectrum, with the median ages of just 37 (1981-85) and 40 (1985-89). Seven of his ministers subsequently ran for the presidency, and his culture minister, Mohammad Khatami, eventually won.

Mousavi was a favorite of the late Ayatollah Khomeini, the orchestrator of the Iranian revolution and its subsequent supreme leader. But Mousavi found himself at odds with his distant relative Ayatollah Ali Khamenei, who was president at the time. Their clashes revolved around economic issues -- Mousavi firmly believing in statist policies while Khamanei favored more private-sector involvement. So heated was their dispute that Khamanei only appointed Mousavi for a second term under pressure from Ayatollah Khomeini. The conflict reached a peak in September 1988, when Mousavi tendered his resignation. Ayatollah Khomeini refused to accept it, deeming it inappropriate amid ongoing cease-fire talks with Iraq. However, less than a year later, the post of prime minister was eliminated entirely to create a stronger presidency. Mousavi's defeat, together with the 1989 death of his patron, Ayatollah Khomeini, pushed him to leave politics.

Political retirement, however, was hardly a retreat into isolation. He advised both Khatami and his predecessor, Akbar Hashemi Rafsanjani, and served as a member of some of Iran's most powerful institutions - notably, the Expediency Discernment Council (1989-present), which supervises  the government and advises the supreme leader, and the Supreme Cultural Revolution Council (1996-present), which sees that cultural, educational, and research policies are in accordance with the values of the Islamic state. Since 1999, Mousavi has been president of the Iranian Academy of Arts, earning a reputation for adopting a more accommodating and diverse definition of artistic expression.

More than 470 people have registered to run against Ahmadinejad, but the Guardian Council, the conservative-dominated body that supervises the elections, is expected to approve less than 1 percent of the would-be candidates. Among those chosen few, Mousavi will pose the most serious challenge to Ahmadinejad.

Mousavi's supporters argue that his track record of successfully managing the war economy proves he could do a much better job on economic issues than Ahmadinejad. Furthermore, they point out that having served as a foreign minister, albeit only for a few months, he is more attuned to the niceties of diplomacy. He enjoys the support of Khatami, powerful anti-Ahmadinejad clerics, and various reformist politicians and organizations.

But Mousavi is certainly no shoe-in. In addition to his political limitations, he is being challenged by Mehdi Karoubi, the former speaker of parliament, who will inevitably split some of the reformist vote. His liberal detractors emphasize that the Mousavi government oversaw the mass execution of political opponents in 1988, and say he has been largely silent on human rights violations since. They also point to his support for Khomeini's fatwa against Salman Rushdie, the British author of The Satanic Verses. Mousavi's mindset is often characterized as a throwback to the early years of the revolution, when Islamic economics, shared sacrifice, and self-reliance were the political norm.

If these critics and an apathetic youth population decide to boycott the elections, Mousavi's sojourn into the realm of active politics will be rather fleeting. But should he succeed in capturing the imagination of the Iranian public, the world could expect a President Mousavi who fits somewhere between the accommodating reformism of Khatami and the strident nationalism of Ahmadinejad. He would not back down from asserting Iran's right to enrich uranium. He would welcome improved relations with the United States but bargain fiercely in any negotiations. Domestically, his enthusiasm for civil society and political freedom would be no match for Khatami's.

Regardless the odds, Mousavi seems set on his run. Perhaps he views now as his best, or even only, chance to win the presidency. In Iranian weddings, the cleric officiating over the nuptials asks the bride three times whether she is willing to marry the groom. It is customary for the bride to stay silent until finally saying "I do" after the third query. Today, after ignoring calls to enter the presidential race in 1997 and 2005, Mousavi has decided to say "I do."

*This updates a previous version that said Mousavi was 68.