October 31, 2009 Abdullah threatens boycott, muddles Afghan runoff Play video

(NECN/ABC: Kabul, Afghanistan) - President Barack Obama has called it the most important moment in Afghanistan this year. But the fate of the election may hang in the balance of one man.

Challenger Dr. Abdullah Abdullah is threatening to boycott Saturday's runoff because he accuses President Karzai of trying to steal the second round.

This vote was only necessary when more than a third of Karzai's ballots in the first round proved fake. Abdullah complains there are no assurances the runoff will be any fairer.

"We want to make sure that the process is healthy and we are not going to be involved in frauds taking place agai," Pro-Abdullah Member Sabrina Sahqeb said.

The United States is cautiously optimistic and hopes that even if Abdullah leaves the race, the process will create a legitimate government.

"We see that happen in our own country where, for whatever combination of reasons, one of the candidates decides not to go forward," Secretary of State Hillary Clinton said.

But critics doubt whether this process will create a legitimate, stable government -- one of the main considerations for President Obama as he weighs his strategy in Afghanistan.

Poor governance has helped make 2009 the most deadly year of the war for both troops and civilians.

This week the Taliban proved they could strike anywhere, anytime, when they killed five inside a United Nations guest house in one of the most secure parts of the

"We have the occasional failures," Chief National Directorate of Security Armirullah Saleh said. "But if you look at the overall picture, we have largely changed the trend."

But right now, there is more fear and uncertainty for a country desperate to finish a long, drawn out election.

ABC's Nick Schifrin reports.