Factbox - Iran's presidential election process

ANKARA (Reuters) - Iranians will vote on May 19 in a presidential election in which pragmatist President Hassan Rouhani is seeking a second term against challengers who criticise his handling of the economy in spite of the lifting sanctions under a nuclear deal in 2015. Supreme Leader Ayatollah Ali Khamenei holds ultimate authority in Iran, but the presidential vote will influence the image and policies of the Islamic Republic. Since 1989, all three predecessors of Rouhani had served two consecutive terms. Following are details of the election and the voting process: - Six candidates were cleared to run for president by Iran’s hardline constitutional watchdog, the Guardian Council, out of 1,636 who registered to enter the contest. About 30 of the registered hopefuls were known political figures. - The Guardian Council is a panel of six senior clerics and six Islamic jurists which vets aspiring candidates in all elections. - To qualify as a candidate, presidential hopefuls must be of Iranian origin and an Iranian citizen, be considered a distinguished political or religious figure and have an unblemished record of piety and fidelity to the Islamic Republic. - The Guardian Council bars women from standing although some top clerics and human rights lawyers argue that the constitution does not exclude them. - The presidential election campaign begins on April 21 and will end at 03:30 GMT on May 18. - All Iranians aged over 18 can vote, which means over 55 million of Iran's more than 80 million people are eligible to vote. - All ballots will be counted manually so the final result may not be announced for two days, although partial results may appear sooner. - If no candidate wins at least 50 percent plus one vote of all ballots cast, including blank votes, a run-off round between the top two candidates is held on the first Friday after the election result is declared. (Writing by Parisa Hafezi; Editing by Richard Lough)