As well as Sayyaf, General Abdul Rashid Dostum, the notorious Uzbek strongman is lined up to be vice-president of one of the front-runners.
He stands accused of allowing hundreds of Taliban prisoners to suffocate to death in shipping containers as well as a string of other alleged war crimes.
Of the 11 candidates who entered the race, six of their candidates or their running mates are regarded as a warlord.
Men like Sayyaf could have a decisive role to play.
Although unlikely to win, he will garner decisive votes that can be put behind one of the two candidates that make it to a run-off, said Fabrizio Foschini, of the Afghanistan Analysts Network.
"He will not win, but he will be one of the next on the list," he said. "That means his part in a run-off will be very important."
Sayyaf, who is in his 60s, has been keen to broaden his appeal.
The 9/11 Commission Report described him as mentor to Khalid Sheikh Mohammed, the mastermind behind the attacks on the Twin Towers, but today Sayyaf is one of the strongest anti-Taliban voices in the country. He has even said he will work with the West, signing a deal to allow American forces to stay in the country beyond the end of the year.
At rallies, he has taken pains to explain how he would protect women's rights, a concept he tends to conflate with "dignity". At another rally event he pointed to a handful of ghostlike blue burkas seated to one side of the stage.
"Women, you know we will defend your rights and your dignity," he said, going on to explain that he was in favour of female doctors and teachers, and wanted to provide a good atmosphere for their education - interpreted by analysts familiar with his ties to Saudi Arabia as a euphemism for separate schooling.
To protect women, he said, he would remove their images from soap boxes.
His deeply conservative message strikes a chord in rural areas. But in Kabul you need not look far to find evidence of his brutal past, when his forces killed thousands of Hazaras - Shias viewed as infidels by Sunni hardliners - as part of a struggle for the city in the Nineties.
Human Rights Watch concluded he was responsible for war crimes.
One of the worst hit areas was Afshar. Dozens of Sayyaf posters have been defaced, ripped so that his familiar beard is shortened or his face disappears completely.
One wizened man, sitting outside a grocery store, was too nervous to discuss Sayyaf without also condemning other candidates. He said: "Sayyaf did these things, but can you tell me which of the candidates does not have blood on his hands?"
Yet this year's election is a crucial test of the country's young democracy. If it passes off without incident, it would represent the first peaceful transfer of power in Afghanistan's history.
The remaining Nato combat forces are departing this year, leaving responsibility for security in the hands of local forces.
A legitimate government in Kabul is key to the exit strategy and one of the most effective bulwarks against the Taliban insurgency. All the front-runners would be acceptable to Western governments, offering varieties of largely ideology-free pragmatism.
Abdullah Abdullah is the main opposition candidate, having refused to do a deal with Mr Karzai after finishing runner-up in 2009.
Ashraf Ghani, a former World Bank official and finance minister, is a safe pair of hands with the economy and has benefited from an energetic social media campaign.
The man to beat is Zalmai Rassoul. He stepped down as foreign minister last year to run and has attracted big name endorsements, including the president's brother, leaving no one to doubt he has the backing of Mr Karzai - and all the benefits that brings.
If the outcome remains uncertain, then the prospect of violence and fraud remain certainties. Twelve million people are registered to vote at more than 6,000 polling stations.
The Taliban have made clear their opposition, claiming that "pious people" would not vote. They have promised to attack polling stations, activists and candidates.
Last week, they made good on their threats: first attacking an election commission office, before launching an assault its main headquarters.
Suicide squads have also stepped up attacks on other high-profile sites, particularly places were foreigners congregate in the capital.
The second major concern for voters is fraud. Only 25 per cent believe the elections will be free and fair, according to a recent poll.
Insecurity means rigging will go in areas unreached by monitors and several candidates have accused Mr Karzai of filling election posts with placemen to deliver the result for his chosen successor.
Western officials and they admit that things will not be perfect.
Rather than pushing for free and fair elections, diplomats and generals talk of "transparent, inclusive and credible".
As one diplomatic source put it:
"It won't be Switzerland, but that does not matter so long as the result is acceptable to Afghans."
