The commissions have until May 14 to certify official results.

Unsurprisingly, the candidates who are behind in the vote count have focused attention on the fraud. At a recent news conference, Mr. Ghani complained that election officials were releasing results without having filtered out fraudulent votes first. “No one can claim that the votes are clean,” he said.

In an interview on Thursday, Mr. Abdullah ruled out any sort of coalition government with Mr. Ghani. “Now the issue is how to strategize for the second round — no matter what, it will go to the second round,” said Mr. Abdullah, who is reported to be in negotiations with other candidates to offer them positions in his government in exchange for second-round support.

Election officials and observers have generally agreed that this year’s presidential election was cleaner than past ones. But when it comes to electoral fraud, Afghanistan has established a pretty low bar.

In the last presidential election, in 2009, voters in some areas were rounded up by armed warlords and herded to the polls, where the votes they cast were checked to make sure of their obedience. In other areas, entire voting districts returned thousands of votes with 100 percent of the ballots marked for a single candidate, even though all the voting places in those districts were closed because of security threats.

In this election, computerized bar-coding of ballots, boxes and tally sheets should make it easier for the authorities to segregate tainted votes. But ballot-box stuffing remained a widely reported problem.

“Fraud is a fact in all elections, and it is especially bad where there is a lack of education,” Mr. Mohseni said. “But in Afghanistan, maybe some people here do some special fraud.”

This year, more indelible ink, a blue silver-oxide blend, was introduced to prevent the multiple-voting problem widely seen in 2009. The new ink is supposed to last several days and be more resistant to erasure.