On June 12 Iranians head to the polls to decide the future of the Islamic republic as hardline incumbent President Mahmoud Ahmadinejad, a fellow conservative, a moderate and a reformist go head to head in what could be a major change in Iranian politics.
After being cleared by Iran's electoral watchdog the Guardians Council Ahmadinejad will face former Revolutionary Guards chief Mohsen Rezai, former premier Mir Hussein Mousavi and ex-parliament speaker Mehdi Karoubi. This year's elections will see the Islamic Republic break with tradition as state-run television began broadcasting debates by the candidates.
Following is a background on each of the four candidates:
Ahamdinejad has earned notoriety around the world for his controversial comments on Israel, his public defense of the Palestinian cause and his rejection of any concession over Iran's nuclear program but his economic policies have also made him controversial at home.
Critics charge that a series of expansionary budgets since his election in 2005 have stoked inflation while doing little to create jobs but Ahmadinejad is standing on a populist platform again this time promising new measures to give ordinary Iranians a share in the country's oil wealth.
Aged 52 and married with two sons and one daughter, Ahmadinejad presents himself as an ordinary man -- normally casually dressed in just a shirt and jacket in contrast to the black robes of Iran's clerical leaders.
The son of a blacksmith, he is known for simple living and for hard work -- he is reportedly often seen in the office at 5:30 am and working until midnight.
World powers want Iran to suspend uranium enrichment to allay Western suspicions its nuclear programme is cover for a drive to produce a bomb but Ahmadinejad insists the programme is a "train without brakes and no reverse gear."
A conservative critic of Ahmadinejad who says he is standing as an independent, Rezai headed Iran's ideological shock troops, the Revolutionary Guards Corps for 16 years and has impeccable hardline credentials.
He was appointed Guards commander by the Islamic Republic's founder Ayatollah Ruhollah Khomeini at the age of just 27 and led the corps during the bloody eight-year war with Iraq.
He is one of five leading Iranian officials wanted by Argentina on suspicion of involvement in a 1994 bombing against a Jewish organization that killed 85 people.
Since stepping down as Guards chief in 1997, Rezai has been the secretary of Iran's top political arbitration body, the Expediency Council.
Now 54, he has been an outspoken critic of the incumbent president accusing him of pushing Iran to the edge of a "precipice."
Rezai, who holds a Ph.D. in economics, has taken particular issue with Ahmadinejad's economic policies and has vowed to do more to rein in inflation and its impact on the purchasing power of the poor.
Mir Hussein Mousavi
Mousavi is a former prime minister widely remembered for his efficient handling of the economy during the brutal eight year war with Saddam Hussein in the 1980s but has been out of the political limelight since then.
A soft-spoken man, who calls himself a "reformist who refers to the principles" of the 1979 revolution that toppled the US-backed shah, Mousavi has the support of reformist former president Mohammad Khatami in his bid for a political comeback.
He has promised that if elected he will seek to change the "extremist" image that Iran has earned abroad during Ahmadinejad's presidency and has not ruled out the possibility of negotiating with U.S. President Barack Obama.
But he has warned that that does not mean he is going to make concessions on Iran's nuclear programme. "I do not think any government will dare to take a step back in this regard," he told a news conference last month.
Now 67, Mousavi has played a behind-the-scenes role in politics over the past two decades, acting as a presidential adviser from 1989 to 22D5 and serving on the Expediency Council.
A former speaker of parliament, Karoubi is the most overtly reformist of the four candidates but insists he has learned the lessons of Khatami's presidency between 1997 and 2005 and will be careful not to antagonize hardliners within the regime.
He says Khatami's presidency, in which Iran pursued a "dialogue of civilizations" that led to a thaw in relations with the West, was a "golden opportunity" missed by reformers and that if elected he will seek to adopt a "middle path."
Promising to adopt a "policy of detente" with other countries, Karoubi says he planned to attract foreign investment and open the Iranian economy, which is 80 percent state controlled, to the private sector.
Karoubi has also vowed to undertake social reforms in a country where strict moral policing has created deep divisions and anger, especially among women and youth.
But he too warned that the West should not expect concessions on Iran's nuclear programme if he is elected as such strategic issues are beyond the remit of the presidency and decided by supreme leader Ayatollah Khamenei.