t was the British-trained surgeon’s success in winning votes from both sides of Iraq’s sectarian divide that delivered his narrow two-seat victory.
First though he will have to prove his bargaining skills in Iraq’s political bazaar, if he is to forge a coalition government from its disparate factions.
Prime Minister Nouri Maliki remains in the race and may yet hang on to his job by appealing to his fellow Shias.
He is talking to the same groups, trying to build his own coalition, while also insisting on a recount - despite the UN declaring the elections credible.
Mr Maliki - who remains caretaker prime minister in the meantime - says he will pursue his challenge by legal means.
The Americans are watching closely, with their withdrawal plans dependent on a relatively trouble-free outcome to the elections.
It is widely thought they would like Dr Allawi to win, although they are being careful to voice no preference.
Mr Allawi has deep ties with the Americans and also with Britain - he worked with both the British and US intelligence services against Saddam Hussein.
Dr Allawi’s narrow two-seat victory over Mr Maliki and his State of Law bloc was an astonishing comeback.
He was shunned by voters as an American puppet in the last general elections, after serving as the first post-US invasion prime minister.
A secular Shia who has criticised Iranian influence on Iraq, he timed his return well.
By allying with Sunni groups, he was able to tap into their sense of being marginalised by Mr Maliki’s Shia-dominated government and its perceived leanings towards Tehran.
Yet while Iraq’s Sunni minority delivered most of his support, Dr Allawi also succeeded in reaching across the sectarian divide and picking up many votes from Shias disenchanted with the prime minister.
A closer look at the results tell the story.
In the southern Shia provinces where Mr Maliki won the bulk of his seats, Dr Allawi still got 10 for himself - holding off competition from other Shia parties too.
Mr Maliki could not match this cross-sectarian appeal in the predominantly Sunni areas where Dr Allawi did best, winning just one.
Crucially, Dr Allawi also picked up nearly as many seats in Shia- dominated Baghdad as his opponent - effectively sealing his victory.
This still only gave his Iraqiya bloc 91 seats - a long way short of the 163 it needs to form a majority in Iraq’s parliament.
Dr Allawi was quick to say he would work with any party, including the State of Law.
"Our talks with different blocs are already more advanced than many realise," said Rend Rahim, one of his MPs.
With the State of Law meeting the same groups, this is a bidding war between the two blocs.
It is the Kurds and the Iraqi National Alliance, the second largest Shia grouping, now dominated by the cleric Moqtada Sadr, who will play the decisive role.
Together they wield over 110 seats, more than enough to give Dr Allawi or Mr Maliki control of parliament.
The Kurds have had differences with both leaders, so they could go either way.
After Mr Maliki cracked down on Moqtada Sadr’s Mehdi army militia, the two former Shiite allies fell out badly.
But the prime minister has already sent people to talk to Mr Sadr, who is in Iran.
Tehran, which has stayed noticeably quiet so far about Dr Allawi’s victory, is likely to encourage such a make-up.
Among Mr Sadr’s supporters in his Baghdad stronghold of Sadr City, many would prefer this outcome too, despite the past.
Keeping Shias in power is seen as more important.
The Americans and British are drafting a new UN resolution on Iraq. It may be circulated as early as this week.
"We are working with our friends and allies to see if we can get a second resolution," President George W Bush said in Washington.
But he repeated that UN backing, though useful, was not necessary.
In the face of strong opposition from France and other Security Council members, diplomats say the US and Britain are toning down what was supposed to be a very tough resolution.
In other developments:
The Pentagon ordered 28,000 more troops to the Gulf, including the highly mobile 3rd Armoured Cavalry Regiment
Pope John Paul II stressed the role of the UN in the crisis at a meeting with Secretary General Kofi Annan in the Vatican
The UN reported slow progress on interviewing Iraqi scientists in private
Washington warned Turkey time was running out for it to decide whether to allow US troops to deploy on its soil.
But a Turkish Government spokesman said there were still political, military and financial issues to resolve before it could seek parliament’s approval on the matter.
Earlier, Turkey declared that a second UN resolution would be required before it could permit US troops to use its bases.
UK Prime Minister Tony Blair - America’s closest public ally on the issue - has made clear he would like a second resolution explicitly authorising the use of force against Iraq.
Facing deep public hostility at home over his support for war, Downing Street officials hope that a resolution sanctioned by the UN would win over doubters.
Asked about the anti-war demonstrations that drew millions world-wide at the weekend, Mr Bush said war was his last choice but the risk of doing nothing was a worse option.
"Some in the world don’t view Saddam Hussein as a risk to peace," Mr Bush said. "I respectfully disagree."
The Governments of France, Russia and China - who along with the US and Britain wield vetoes in the Council - have also expressed clear reservations about war.
French President Jacques Chirac on Monday said that he would oppose any effort to draft a resolution authorising war at this time, and implied he would be prepared to use the French veto to block it.