Abdullah Abdullah has finally agreed to share power with his rival Ashraf Ghani, who has been named the new president of Afghanistan.
The former foreign minister, who believes that the title of the president has been stolen from him twice, has agreed to be a part of the national unity government.
In accordance witt the deal, Abdullah was sworn in as chief executive, a new role with powers similar to those of a prime minister that was created to break the election deadlock.
Ghani, an ethnic Pashtun, and Abdullah, whose main support comes from the country's second largest ethnic group, the Tajiks, face a difficult task forging unity in a country riven by ethnic and tribal rivalries.
Abdullah's accusations that the run-off election was rigged in Ghani's favour had raised fears of ethnic violence, which could have ignited a broader conflict.
Former ophthalmologist and resistance fighter, Abdullah had earlier charged massive vote fraud and said he was the rightful winner. Abdullah, 53, had also alleged fraud in the 2009 election which he lost to former President Hamid Karzai.
This time, Abdullah an easy winner in the first round with 45 percent compared to rival Ashraf Ghani's 31.6 percent. But the preliminary results of the June 14 second round showed Ghani getting 56.44 percent of the vote.
During the first round too, Abdullah claimed that cheating denied him the 50 percent needed for a first-round victory in April.
As a pro-Western, religiously moderate politician, Abdullah has spent his time in opposition building ties with tribal leaders, as well as staying close to the US.
Abdullah was a member of Burhanuddin Rabbani's government during Afghanistan's 1992-1996 civil war, and made a name for himself abroad for his fluent English and courtly manner.
His formative political experience was as the right-hand man to Ahmad Shah Massoud, the charismatic Tajik commander who led resistance to the Soviet occupation in the 1980s and to the 1996-2001 Taliban regime.
Massoud was killed two days before the 9/11 attacks on the United States, leaving Abdullah fearing that the anti-Taliban resistance would collapse.
But the US reaction to the strikes on New York and Washington transformed the landscape overnight, with the Taliban soon ousted and Abdullah emerging as foreign minister in the new government under Karzai.
Abdullah used the post to give early warning to Washington that Taliban leaders ran the growing Afghan insurgency from Pakistan - an issue that was dismissed until it became central to US foreign policy years later.
Born to a Pashtun father and a Tajik mother, he has long taken a strong stance promoting reconciliation between Tajiks and their tradition rivals the Pashtuns, the largest ethnic group in Afghanistan.
However, due to his closeness to Massoud, much of his core support still comes from Tajik and other Dari-speaking ethnic groups in the north.
His anti-Taliban record could also make starting a peace process with the fighters more tricky.
Abdullah, a persuasive talker and elegant dresser, is married with three children.
On the campaign trail, he delivered scores of professional - if rather dry - speeches at rallies and meetings, often raising the spectre of electoral fraud.