Afghanistan's election commission Monday canceled Saturday's scheduled presidential runoff a day after challenger Abdullah Abdullah pulled out of the race.

Abdullah, whose decision left incumbent President Hamid Karzai as the only candidate, said he was dropping out of the race because he did not think the election would be fair.

Because Abdullah dropped out and eliminated the need for a runoff election, the country's Independent Election Commission declared Karzai the winner, CNN reported.

Karzai was favored to win the runoff, called after ballots from the Aug. 20 election were thrown out when they were determined to be tainted. The election's first round was marred by massive electoral fraud, the BBC reported.

Internationally, the runoff was seen as a way to restore legitimacy to Afghanistan's electoral process, the BBC said.

The cancellation comes as U.S. President Barack Obama weighs whether to send more troops to Afghanistan as requested by Gen. Stanley McChrystal, commander of U.S. and NATO troops in the country.

"We're in a new stage now ... to bring the election politics to an end," former Afghan Ambassador Zalmay Khalilzad told CNN.

Karzai's next steps will provide clues about how he will address questions about the legitimacy of his election and whether his government is strong enough to protect and advance democracy.

"More of the same will send a signal of weakness," Khalilzad said. "But if he can bring an effective government together ... it will be encouraging and will have a positive effect."