The regime's Get Out the Vote video, calling for a high turnout as a "hard slap" to Iran's enemies
There are 290 seats in the Iranian Majlis, with members serving four-year terms. The chamber is officially led by a speaker.
There are no political parties as such; instead, blocs or factions can emerge. The Parliament is dominated by "conservatives" and "principlists", a term usually applied to the political wave since the election of President Ahmadinejad in 2005.
"Reformists", who were prominent in the legislature during the Presidency of Mohammad Khatami (1997-2005), have been squeezed into a weak minority group of about 50-60 representatives. That number is likely to fall sharply in the next Majlis.
In today's first round, voters will choose names from dozens of lists of candidates. Allocated seats range from 30 for Tehran to one for Iran's smallest towns and villages, so a voter in the capital can write up to 30 names whereas the process elsewhere is far simpler.
Any candidate who receives more than 25% of the vote in his/her district is elected. Those who receive less than 25% but above a minimum standard will be on the ballot for a second round of voting in about two weeks. In that ballot, the candidate will have to get "a relative majority" of ballots to enter the Majlis.
THE MAJOR LISTS
This should be prefaced with the note that the lists are not as important today as the individuals who may or may not emerge from them. Because candidates will put themselves on more than one slate, it is not possible to label a group simply as "pro-Supreme Leader" or "pro-Ahmadinejad". And because voters select specific names, rather than an entire list, no single faction is likely to put all its people into Parliament.
The Unity Front (Jebheh Mottahed-e Osoolgaraayaan)
The initial hope of many in the regime was that a single list would be agreed by all conservatives and principlists. A special committee under the head of the Assembly of Experts, Ayatollah Mahdavi Kani, pursued the task last autumn.
The effort was blocked by an emerging faction, the Islamic Constancy/Resistance Front, which objected to a prominent role for certain politicians such as Speaker of Parliament Ali Larijani and Tehran Mayor Mohammad-Baqer Qalibaf.
The Unity Front still has the best-known candidates, and it is generally supportive of the Supreme Leader's vision for Iranian politics. However, there are also members of the list who are sympathetic to Ahmadinejad; indeed, some are on the Islamic Constancy Front's slate as well.
Islamic Constancy/Resistance Front (Jebheh Paaydaari-e Enghlelab-e Eslami)
The Front is led by Ayatollah Mesbah Yazdi, who has been called Mahmoud Ahmadinejad's "spiritual mentor", and many on the list are supportive of the President.
It is far too simple, however, to just label this a "pro-Ahmadinejad" slate. Mesbah Yazdi and others have been critical of the Government and Ahmadinejad's advisors, notably Chief of Staff Esfandiar Rahim-Mashai, and the slate includes former Ministers, such as Kamran Baqeri Lankarani, who were dismissed by Ahmadinejad.
The list may be better considered as a collection of individuals --- again, some of whom are also among the Unity Front's names --- who are looking for room to manoeuvre against rivals among conservatives and principlists.
The Voice of the Nation (Jebheh Sedaa-ye Mellat)
The group is led by individuals who have both been critical of the Ahmadinejad Government and who were turned aside by the Unity Front.
Leading members include MPs Ali Motahari, Hamidreza Katouzian, and Ali Abbaspour, former Minister of Higher Education Hassan Ghafouri Fard, and Alireza Mahjour, the head of the Workers' House.
Motahari, in particular, has drawn attention in the campaign with his sharp challenge to the Government and criticism of the system. He is likely to attract the votes of reformists who do not boycott the ballot in Tehran.
The Steadfastness Front (Jebheh Eistaadegi Enghelab-e Eslami)
The Front is a loose collection of conservatives, many linked by support for Mohsen Rezaei, Secretary of the Expediency Council and a challenger to Ahmadinejad in the 2009 Presidential election. It also includes the names of the "breakaway" conservatives Ali Motahari and Hamidreza Katouzian.
The Front was dented by the Guardian Council, who rejected the candidacy of one of its leading names, Seyyed Mahmoud Alavi, a member of the Assembly of Experts.
The Democratic Front
The Front includes some reformists who have rejected calls not to stand in the election. The most vocal member is Mostafa Kavakebian.
The Front, however, has drawn little attention in the campaign. Its identity --- as well as the position of reformists in the next Parliament --- has been further muddled by reports that Kavakebian has declared that he is now a principlist.