Abdullah Abdullah (center), a prominent Afghan opposition leader, registers his candidacy in next year's presidential election in Kabul, Afghanistan, on Tuesday, Oct. 1, 2013.  The election will be key in helping to determine the success or failure of 12 years of U.S.-led military and political intervention in the country. (AP Photo/Rahmat Gul)

Photo by: Rahmat Gul

Abdullah Abdullah (center), a prominent Afghan opposition leader, registers his candidacy in next year's presidential election in Kabul, Afghanistan, on Tuesday, Oct. 1, 2013. The election will be key in helping to determine the success or failure of 12 years of U.S.-led military and political intervention in the country. (AP Photo/Rahmat Gul)