Iranians go to the polls today to elect a new president. Although the position is not purely ceremonial, it is not the top position in the state either: the supreme religious leader, ayatollah Ali Khamenei (who is appointed for life), holds the real power.

But that doesn’t stop the presidential election from being an interesting contest. For two terms, from 1997 to 2005, the post was held by a reformist, Mohammad Khatami, who was a constant thorn in the side of Khamenei and the conservatives. He was succeeded by Mahmoud Ahmadinejad, whose idiosyncrasies have kept the world entertained and often appalled; his re-election in 2009 was widely believed to be fraudulent and led to a popular uprising that was brutally suppressed. His main opponent, Mir-Hossein Mousavi, remains under house arrest.

As I reported last week, the regime this time has again winnowed the field of presidential candidates considerably. Only eight were approved, and two of those have since withdrawn, leaving six to face the electors. One, ayatollah Hassan Rouhani, is regarded as a moderate; the others are in varying degree conservatives, and most are clearly allies of Khamenei. Ahmadinejad is also on the outer with the supreme leader – his chief-of-staff, Esfandiar Rahim Mashaei, is one of those that the Guardian Council rejected.

If no candidate wins a majority tomorrow the top two contenders will contest a second round a week later (this has only happened once, in 2005).

The general assumption has been that the fix is in for a conservative candidate, most likely Saeed Jalili. Reports this week, however, suggest genuine popular enthusiasm for Rouhani and a rallying behind him of the various strands of Iran’s reformist movement. He is being backed by, among others, former presidents Khatami and Akbar Hashemi Rafsanjani and former first vice-president Mohammad Reza Aref (one of the candidates who withdrew).

The BBC’s Kasra Naji says that

Mr Rowhani is fast becoming the candidate the movement was not allowed to put up. He is pulling large crowds wherever he goes, speaking the language of reform, promising to free political prisoners, guarantee civil rights and promising to return “dignity to the nation”.

At the noisy rallies, the strength of feeling among young Iranians for change is palpable.

At the Atlantic, Shervin Malekzadeh reports similar scenes:

Rouhani’s campaign, working within official regime discourse, is proving to be one of the most subversive in recent memory. More important than picking winners and losers, the central thesis of elections in Iran is that each vote is “a shot to the eye of the enemy,” proof that the Islamic system, with the support of the people, stands strong against the United States. Rouhani doesn’t reject this narrative so much as turn it on its side: Iran must stand firm against the U.S., but it must do so in a way that serves the interests of the nation. …

With the emergence of Rouhani as the consensus candidate on the reformist side, the wave of the electorate appears to be once again breaking against the current regime.

Typically, in countries where the regime is as obviously resistant to public opinion as is Iran’s, opposition forces will contemplate boycotting elections rather than be seen to grant it additional legitimacy. A year or even a fortnight ago one would have said that a large-scale boycott was likely at this election. But now the opposition seems to have come around to making a serious effort – if not to win, then to force Khamenei to engage in open ballot-rigging.

High turnout has always favored the reformists, but the regime also wants a high turnout to bolster its democratic credentials, despite the risk that entails.

The big difference between now and 2009 (apart from the fact that the 2009 experience is now there as a warning to both sides) is that the regime is not united behind a single candidate. Jalili has failed to inspire enthusiasm, and it is suggested that Teheran mayor Mohammad Baqer Qalibaf – also a conservative, but of a more pragmatic stripe – may now be better placed. (Transliteration is variable; he is sometimes spelt Ghalibaf, just as Rouhani is sometimes Rowhani or Rohani.)

Opinion polls in Iran, for obvious reasons, are unreliable, but a recent IPOS poll puts Rouhani in the lead with 31.7% ahead of Qalibaf on 24.1%, followed by Mohsen Rezai (another 2009 candidate) on 14.3% and Jalili on 13.7%. If those numbers are anything like correct, it’s hard to see how a runoff next week can be avoided, with all of the attendant extra publicity and scrutiny – not something that Khamenei thrives on.