(For more Afghanistan and Pakistan stories, click [ID:nAFPAK])
* Commission member quits citing foreign interference
* Fraud percentage no longer calculated for each candidate
* Abdullah accepts new tallying method
(Adds Abdullah comment)
By Peter Graff and Sayed Salahuddin
KABUL, Oct 12 (Reuters) - Afghanistan's election watchdog changed its fraud-tallying rules for the second time in less than a week on Monday, switching back to a formula that lowers the chance of overturning President Hamid Karzai's first-round win.
In a further sign of disarray, one of only two Afghans on the five-member Electoral Complaints Commission (ECC) abruptly resigned. The member, seen by diplomats as a supporter of Karzai, said the commissioners had been subject to foreign interference.
The ECC announced the change in its rules just days before it is due to present the results of its fraud probe, which will determine whether Karzai wins in the first round or needs to face his former foreign minister, Abdullah Abdullah, in a run-off.
Under the new rules the commission will not take into account which candidate it finds benefitted most from any fraud.
The change effectively reverts to initial rules announced last week, which were changed mid-week after being criticised for potentially shielding Karzai.
"It was our mistake in how we interpreted it. We thought we could get more granular, and it turns out that was not the case," the ECC's U.N.-appointed head Grant Kippen, a Canadian, said.
In preliminary results, Karzai won 54.6 percent of the vote. In order to force a second round, the commission would have to find that fraud overwhelmingly benefitted him over other candidates, reducing his share below 50 percent.
The commission has ordered a recount of about a quarter of ballots, about 75 percent of which were cast for Karzai.
Under the new guidelines, the commission has divided the suspicious ballots into six categories based on the reason for considering them suspect, and will disqualify the same percentage of ballots for each candidate from among those in each category.
Last Wednesday the ECC said it would calculate a different fraud percentage for each candidate, so that candidates who benefitted from more fraud would face a greater penalty. That would have made it easier to conclude that Karzai's supporters were far more culpable than his rivals and force a second round.
Under the new rules, the commission could find more than a million fake votes and Karzai would still win squeak through. Under the rules from last Wednesday, Karzai could have faced a recount with as few as 520,000 fraudulent ballots rejected.
Nevertheless, Abdullah told Reuters the commission had explained its new methodology to him, and he accepted it.
"They convinced us that statistically this is the only way," he said, adding that he still expected a second round, based on reports from his staff monitoring the recount.
RESIGNATION DAMAGES TRUST
The ECC is the final arbiter of fraud in the election, and Western governments are counting on it to come up with a result that Afghans will accept as fair, after it found "clear and convincing evidence of fraud".
Three of its five members were appointed by the United Nations, while the other two are Afghans.
In a blow for the body's credibility, one of the Afghans, Mustafa Barakzai, said he was quitting because he believed foreigners were exerting influence over the body.
"When it was proven to me that there was interference, I decided to leave. If there was no interference (the final result) would not have been delayed," Barakzai told reporters, echoing a criticism Karzai has made that foreigners slowed the process.
Barakzai was appointed to the commission by Afghanistan's Supreme Court. A diplomatic source said he was seen as supporter of Karzai and may have quit ahead of the announcement to avoid being associated with a ruling that would require a second round.
Kippen said: "I don't understand what he's referring to in terms of international interference. It's unfortunate, we wish him well and we'll miss his presence." (Editing by Alex Richardson) (For more Reuters coverage of Afghanistan and Pakistan, see: here)