Ethnic Tajik candidate Yunus Qanooni, considered the likely runner-up to interim President Hamid Karzai, made the announcement at his Kabul home on Monday, a day after two other candidates also peeled away from the boycott. He said he had made his decision after a meeting with U.N. representative Jean Arnault and U.S. Ambassador Zalmay Khalilzad.
"I don't want to be against the election and I appreciate the good will of the people of Afghanistan," Qanooni said. "I want to prove to the people of Afghanistan that the national interest is my highest interest."
The announcement was a huge victory for election organizers, who agreed to set up the panel on Sunday in hopes it would end the crisis that emerged when all 15 opposition candidates announced the boycott — in the middle of Saturday's voting.
Massooda Jalal, the only female candidate, and ethnic Hazara candidate Mohammed Mohaqeq said Sunday they would end their boycott in favor of setting up the panel.
Meanwhile, an exit poll conducted by an American nonprofit group found that interim President Hamid Karzai won Saturday's election with the outright majority needed to avoid a second round.
The survey by the International Republican Institute, which is closely tied to the U.S. Republican Party but not directly affiliated with it, found Karzai ahead of Qanooni by 43 percentage points. The group would not give specific vote totals for either man, nor did it release supporting data.
It based its findings, which organizers called "preliminary," on 10,050 survey responses from its workers in the field.
The survey was paid for by the U.S. Agency for International Development.
A senior Western official who met with some of the 15 candidates on Sunday said many had decided to back down and support the investigative team.
"Some of the candidates say they made that statement (the boycott) in too much of a rush," the official said on condition of anonymity. "They are now looking for a way out that allows them to save face."
Election observers, the U.S. Embassy and Karzai have all sought to put the best face possible on the vote, noting that Taliban rebels were mostly silent and that turnout was high in a nation that has never before tasted democracy.
"The numbers and enthusiasm both were very, very great. It was unbelievable. A day of celebration, really, for the Afghan people," Karzai said Monday on NBC's "Today" show. "People braved attacks by terrorists and went to the election. ... This is really a victory of the Afghan people over terrorism."
Karzai added that the election should be a slap in the face to Osama bin Laden and his al Qaeda followers.
"This election ... is a strong reminder to him that people don't want them, that the people want a different life. So he should be much more afraid today than he was the day before yesterday or before that. He must be trying to hide even in a tighter place than he was a few days ago. We will find him one day, sooner or later," Karzai said.
Boxes of ballots, some arriving by mule, were not expected to finish reaching counting centers until at least Tuesday.
Before the tallying of votes can start, the numbers of received ballots are checked against a list of votes cast to ensure none of the ballot boxes have been stuffed with fraudulent votes, U.N. officials said.
Then, the ballots from various districts are mixed together so no one knows which area favored which candidate.
Actual counting may not start until Wednesday or Thursday, said electoral spokesman Sultan Baheen. Aykut Tavsel, another electoral spokesman, said candidates have until Tuesday evening to file formal complaints, and that the commission doesn't want to start the count until after it has reviewed them.
Final results were not expected until the end of October.
"The counting will be done in full view of cameras," Karzai told NBC. "Afghan television will telecast it direct from the counting stations. I am confident enough the count will be conducted properly."
Security chiefs in the provinces and Baheen said no major attacks had been reported on the transporting of the ballot boxes.
The top U.S. commander in Afghanistan, Lt. Gen. David Barno, told The Associated Press the election could sound the rebels' death knell, and that Taliban leaders might "eventually look for ways to reconcile with the government that comes in."
Poll organizers decided Sunday they would form an independent commission to investigate the weekend balloting.
"There is going to be an independent commission made to investigate it," electoral director Farooq Wardak said. "There could be mistakes; we are just human beings. My colleagues might have made a mistake."
The panel will include former Canadian diplomat Craig Jenness and Staffan Darnolf, a Swedish election expert. The third member was yet to be announced, officials said.
The opposition complaint was focused on allegations that the supposedly indelible ink used to mark voters' thumbs in some polling stations could be rubbed off, allowing some people to vote more than once.
The opposition protest was an embarrassment to the international community, which spent $200 million putting on the election. It could also stain a vote that President Bush has hailed on the campaign trail as a symbol of the success of his war on terrorism.
Mr. Bush has pointed to the 10.5 million Afghans who registered as evidence of that success. But critics note that the figure is close to the total number of eligible voters, suggesting the possibility of fraudulent registrations.
Saturday's presidential election was postponed twice, and the parliamentary vote that was supposed to accompany it has been put off until next spring at the earliest.