Many were dubious when the little-heralded Shiite politician came to power in 2014 as the jihadists' rampage across the country placed Iraq's very existence in doubt.

As Baghdad clawed back territory in a bloody campaign -- rebuilding its shattered forces -- his stock began rising both at home and abroad.

In the run-up to elections Saturday, the stocky 66-year-old was seen as the frontrunner to claim a new four-year term.

But with the results coming in, it seems voters punished him for his failures on another front -- failing to live up to a vow to tackle Iraq's endemic graft.

"If he had kept his promise then he would have got a second mandate with the support of all the people," shopkeeper Amer al-Ameri told AFP in Baghdad.

"He missed a golden opportunity."

- 'I will, I will' -

Widely nicknamed "I will, I will" by a populace long tired with the empty pledges of out-of-touch rulers, Abadi could never shake his reliance on Iraq's old political elite.

"He was not brave enough to tackle the symbols of corruption, despite the major popular support," said journalist Kazem Ajrich.

Abadi fashioned his own Victory Alliance coalition for the parliamentary poll but drew heavily from the ranks of his establishment Dawa party, which has dominated Iraq.

"He chose to surround himself with Dawa people," said political analyst Hisham al-Hashimi.

Infighting between Abadi and his predecessor as premier Nuri al-Maliki -- who heads Dawa -- seriously dented the reputation of what has been the preeminent force in Iraqi politics.

Despite railing against Maliki -- widely reviled for losing ground to IS and stirring sectarianism -- Abadi failed to really distance himself.

"The list of candidates Abadi put forward was full of people who have been in power for 15 years and were accused of having done nothing during that time," said Hashimi.

Instead of choosing Abadi's list voters apparently either opted to stay home -- with turnout at a record low of 44.5 percent -- or opt for candidates who portrayed themselves as anti-establishment.

Tackling graft was one of the key demands in one of the most corrupt country's in the world.

But it was under Abadi -- who has an engineering degree from Britain's Manchester University -- that an amnesty was passed allowing tainted officials to escape jail.

- Economic toll -

Seen as a compromise figure, Abadi has balanced off key players the United States and Iran and was widely favoured by the international community.

He invited a US-led coalition to help roll back the jihadists and kept up good ties with Tehran.

The complex arithmetic and Byzantine machination of the Iraqi political system mean that he could still emerge again as a consensus pick for PM -- albeit seriously weakened.

Abadi's record on the economy failed to convince Iraqis as the country embarks on the mammoth task of rebuilding after the war against IS.

"His decision to reduce the salaries of civil servants despite a rise in oil prices and privatise the electricity sector known for corruption played into this," said commentator Mahmoud al-Dawud.