Iraqis started voting on May 12 in the country's first parliamentary elections since Baghdad declared victory over the Islamic State (IS) and routed the extremist group from most Iraqi territory last year.
Prime Minister Haidar al-Abadi, a Shi'a who has sought to balance the competing influences of Washington and Tehran, is marginally ahead in opinion polls ahead of the vote.
Abadi's Victory Alliance list got a big boost in the polls from public approval of his proclaimed victory in December over IS, which at one point in 2014 occupied one-third of Iraq's territory.
Polls show Abadi also won approval for forcefully putting a stop to a bid by Iraq's autonomous Kurdish region to declare independence last year. But he lacks charisma and has been blamed for failing to improve the economy.
Abadi also cannot rely solely on votes from the Shi'ite community to win another term in office, as Iraq's majority Shi'a are unusually split this year between three rival candidates.
Making up for the lack of united backing from Shi'a, polls show Abadi has drawn an unusual level of support in the northern city of Mosul and other areas dominated by Sunnis who were liberated from IS.
Abadi's two main challengers, also Shi'as, are his predecessor Nuri al-Maliki and Iranian-backed Shi'ite militia commander Hadi al-Amiri. Both rivals are seen as closer to Tehran than Abadi.
When he was prime minister, critics say Maliki's pro-Shi'a policies created a polarized atmosphere that enabled IS to gain sympathy among Sunnis as it swept across northern and western Iraq in 2014.
In his comeback attempt, Maliki is promising to strengthen the role of Shi'a in Iraq's government once again.
His rival Amiri spent more than two decades fighting Saddam Hussein from exile in Iran and speaks fluent Farsi.
Amiri leads the Badr Organization, which was the backbone of the volunteer forces that helped to defeat IS along with Iraqi government troops and U.S.-backed Western coalition forces.
Amiri hopes to capitalize on his battlefield successes. Victory for Amiri would be seen as a big a win for Iran, which has sought to increase its influence in Iraq and the wider region.
After the fall of Saddam in 2003, decades of dominance by his Sunni-led Baath party came to an end and senior government positions were unofficially split between Iraq's three main ethnic and religious groupings.
The post of prime minister was reserved for a Shi'a, the parliamentary speaker is Sunni, and the ceremonial presidency has gone to a Kurd. All three posts are chosen by parliament.
In the elections, nearly 7,000 candidates, including 2,011 women, are vying for seats in the 329-member parliament.
The splits among the country's Shi'ite factions make it unlikely for a single party to secure enough seats to form a government on its own.
Some 22.5 million Iraqis are eligible to vote, according to official figures. Official results are expected to be announced on May 13.
Iraqi authorities have tightened security for the election, amid fears of attacks by IS remnants. Last month, IS threatened to attack Iraq's polling stations, saying any participant in the vote would be targeted.
Cells thought to be linked to the radical group have mounted scattered attacks across Iraq since Abadi in December declared the recapture of all territory seized by the extremists.
As a result, some 900,000 police and soldiers have been deployed to secure voting places. The country's border crossings and airports also were closed at midnight on May 11 and will stay closed until the end of the one-day balloting.