KABUL, Afghanistan — When the campaign team led by Manawar Shah came under threat on the day of the Afghan presidential runoff, it was not from the Taliban, he said, but from the people who were supposed to be keeping order: an alliance of government officials, security forces and supporters of candidate Ashraf Ghani Ahmadzai.
Beaten and prevented from using their video equipment and cell phones, his team members, working for candidate Abdullah Abdullah in Khost province, spent June 14 watching fraud but unable to document it. In one polling center, Mr. Shah said, they saw just 500 voters and election officials casting multiple ballots, for a total of 10,531 votes.
That episode and others like it led Mr. Abdullah to level accusations of a conspiracy by Mr. Ahmadzai, election officials and President Hamid Karzai to rig the vote, plunging the country into crisis and creating a new threat of factional violence. After years of Western aid spent building it, the Afghan state is suddenly at risk of collapsing just as U.S. troops are leaving.
The impasse grew so grave that some senior Afghan officials considered imposing an interim government — a move tantamount to a coup, but one the officials insisted might be needed to head off violence.
Mr. Ahmadzai and Mr. Karzai have denied Mr. Abdullah’s accusations. But interviews with Afghan and international officials support some of the most serious of Mr. Abdullah’s claims, offering new details of a broad effort to push the runoff to Mr. Ahmadzai, including a pressure campaign by election and palace officials and ballot-box stuffing orchestrated by an ally of Mr. Karzai. Most spoke on the condition of anonymity to avoid offending senior Afghan officials.
The huge scale of the fraud — involving perhaps more than 2 million ballots out of roughly 8 million reported cast, according to independent international estimates — has stymied efforts to achieve a democratic transition. Secretary of State John Kerry has intervened twice to keep the campaigns in agreement on a unity government and a complete audit of the vote, but the process has repeatedly broken down in disputes.
Despite the hopes that drove millions of Afghans to cast legitimate votes to choose a president, the extent of the fraud has ensured that even if the process comes to a peaceful conclusion, the result will look less like an election correction than a brokered result. And in recent days, officials have quietly expressed worries that even keeping the peace may be difficult.
The warning signs have been there since the 2009 presidential election between Mr. Karzai and Mr. Abdullah, when 1.3 million fraudulent ballots were thrown out. Deeply angered by Western handling of that election, Mr. Karzai pushed changes to the election commissions and the electoral law, removing the international delegates from the complaints commission, appointing new commissioners and outlawing a statistical method used for identifying fraud.
As the election approached, Mr. Karzai avoided public statements for or against any specific candidate, and insisted he was staying out of the process. The president did, however, make an important introduction.
Early on, Mr. Karzai referred an operations officer to the Independent Election Commission, describing him as his “nephew” — an expression of his favor rather than of actual kinship. The official’s name was Zia ul-Haq Amarkhail, an energetic young officer who had worked in the field operations of the commission for two years and knew his way around the system.
He was promptly appointed head of the secretariat of the commission, putting him in charge of electoral operations. One official who works inside the election commission said Mr. Amarkhail met frequently with senior aides to the president at the palace, though election officials were supposed to guard their independence.
Early during the election dispute, Abdullah campaign officials offered a series of audio recordings in which they say Mr. Amarkhail, other election officials and Ahmadzai campaign workers can be heard directing various officials in ballot-box stuffing. That identification has been supported by a number of Western and Afghan officials who say the recordings are from direct intercepts of telephone calls.