Four contenders register for Iran's presidential elections on June 12, 2009

Presuming that four main candidates compete, a run-off is a certainty. In the last run-off, which brought Ahmadi-Nejad to office when he defeated Hashemi Rafsanjani in 2005, the cleric and candidate Mehdi Karroubi complained loudly of interference in the balloting. In fact, Karroubi claimed that he, not Rafsanjani should have been in the run-off. Some of his supporters argued that Ahmadi-Nejad's supporters, not least Supreme Leader 'Ali Khameinei, preferred Rafsanjani as an easier to defeat rival, given widespread knowledge of his corruption. Karroubi is running again, and he has issued pre-emptive warnings about his demand for an unfettered election.

So, it will be Karroubi or Mir-Hossen Moussavi (supported by former President M. Khatami) vs. Ahmadi-Nejad or Mohsen Rezaei, the former Pasdaran commander. My hunch is Ahmadi-Nejad's showerings of patronage will buy him a lot of popular support, while former Prime Minister Moussavi will find more support than Karroubi (the office of Prime Minister was abolished in Iran more than two decades ago); however, Iran's elections, despite the systematic tampering by the regime, are not always very easy to call. Khatami's 1997 election was a complete surprise, and Ahmadi-Nejad's victory was not widely either.

FT.com / Iran - Four contenders register for Iran polls

"Mr Karroubi, the most outspoken reformist amongst the candidates, called on the interior ministry, which is in charge of holding the election, to protect the integrity of the voting system.

"“I have come to run in a free election without the interference of basij, armed forces and rogue agents,” Mr Karroubi said, vowing to stand “firm” against any irregularity.

"The basij, the 10m-strong voluntary arm of the Revolutionary Guards, played a crucial role in mobilising Iranians to vote for Mr Ahmadi-Nejad in 2005. Reformists say this runs counter to the constitution which bans military groups from interfering in politics."