FACTBOX: Iran parliament vote campaigning starts

(Reuters) - Iranian politicians launched campaigns on Thursday for the March 14 parliamentary election that will test President Mahmoud Ahmadinejad's popularity.

Conservatives are expected to keep control of parliament but analysts say incoming lawmakers are still likely to be more critical of the president, partly because many will be jockeying for position before the 2009 presidential vote.

Pro-reform politicians, the staunchest opponents of the president, have been battling to make a comeback, seeking to capitalize on popular discontent over Ahmadinejad's handling of the economy and surging inflation, now around 19 percent.

But they say their chances of expanding their small minority in the 290-seat parliament have been dashed by an official vetting process that has barred many of them from running.

Following are some facts about Iran's eighth parliamentary election since the 1979 Islamic revolution:

* QUALIFICATION OF CANDIDATES:

-- Candidates faced a screening process, first by government-controlled executive bodies and then by the Guardian Council, a conservative body that vets hopefuls on criteria such as commitment to Islam and the Islamic Republic.

-- About 4,500 candidates were approved out of about 7,600 who applied.

-- Reform-minded politicians see disqualifications as an attempt by hardliners to keep them out of power. The Council denies bias and Ahmadinejad's backers and other conservatives dismiss complaints and say the race will be competitive.

* CAMPAIGNING

-- Iran does not have a tradition of disciplined party membership or detailed party platforms but, after months of haggling, three main groups -- two conservative and one pro-reform -- have emerged in the fight for parliament.

They are:

-- UNITED FRONT: The biggest conservative group includes both supporters and opponents of Ahmadinejad but is seen as the most pro-government of groups issuing a candidate list. It is expected to win most seats. Topping the list is Parliament Speaker Gholamali Haddadadel, who publicly clashed with the president shortly before the election over a legislative issue.

Conservatives often call themselves "principle-ists" or "principle-oriented" politicians because they see themselves as upholders of the Islamic Republic's principles.

-- INCLUSIVE COALITION: This conservative group includes Ali Larijani, who quit as chief nuclear negotiator last year citing differences with Ahmadinejad. It also includes backers of Tehran mayor Mohammed Baqer Qalibaf. Both lost to Ahmadinejad in the 2005 presidential race and may still eye the presidency.

-- COALITION OF REFORMIST GROUPS: Reformists were led to power by Mohammad Khatami when he won the presidency in 1997. By the time he left office in 2005 after a maximum two terms, reformists had lost parliament and his reforms had fizzled out in the face of opposition from the conservative establishment. Reformists back social and political change but, except for a more radical wing, support principles of the Islamic Republic.