Abdullah Abdullah's refusal to take part in the Afghan presidential election runoff on November 7 is a watershed event. From his point of view, the former foreign minister did the sensible thing, having carefully assessed he had no stake whatsoever in a runoff that he had zero chance of winning.
President Hamid Karzai has also shown the door to Abdullah's Western sponsors. They had approached in hopes of gaining a last-minute "deal" that would see Abdullah, their protege, gain some position in the future administration. Abdullah saw that from this point onward, the law of diminishing returns would be at work if he kept pecking at Karzai.
Karzai estimated that Abdullah would be a thorn in the flesh - or worse still, a Trojan horse for the Western powers; having him in the government in any serious capacity would result only in Karzai spending sleepless nights at the presidential palace.
In any case, Karzai calculated that Abdullah had already inflicted the maximum damage possible by lending his services to the president's Western detractors. Karzai also knows that he will continue to enjoy strong support from within the major non-Pashtun groups as long as his partnership with erstwhile mujahideen leaders Mohammed Fahim, Karim Khalili, Ismail Khan, Rashid Dostum and Mohammed Mohaqiq remains intact.
http://www.atimes.com/atimes/South_Asia/KK03Df04.html