The results of the races for the relatively weak legislature are unlikely to affect Karzai, who has passed much legislation by decree when parliament was in recess.
But the perception of how the vote is conducted will reverberate strongly with the international coalition supporting Afghanistan with 140,000 troops and billions of dollars.
The election will also be an indicator of the strength of the insurgency as NATO and Afghan forces work to secure polling stations in volatile areas amid Taliban threats against voters and election workers.
Hardly anyone is predicting a free and fair vote by Western standards.
"This is probably one of the worst places and the worst times to have an election anywhere in the world. We have to put it into perspective," said Staffan de Mistura, the top U.N. envoy to Afghanistan.
"We don't expect a fair and transparent election. What we expect is an acceptable election," said Haroun Mir, director of the Afghanistan Center for Research and Policy Studies, a Kabul-based think tank.
The hope is that Afghans and the international community will be able to proclaim it an improvement over the August 2009 presidential vote, when a U.N.-backed anti-fraud watchdog found rampant fraud in Karzai's re-election.
"It does need to be perceived, and seen and felt, by the Afghans and by the international community as less fraudulent," de Mistura said.
Although Western observers have questioned Karzai's commitment to combating corruption, they say they are pleased with the steps taken by the Afghan government to strengthen the independence of its election commission and the decision to announce polling stations a month ahead of time - eliminating much of the confusion that enabled officials to stuff ballot boxes and change tallies in 2009.
"The preparations are miles better than they were last year," said Mark Sedwill, NATO's senior civilian representative.
But a new U.S. watchdog report warns that it will take years to solve certain problems in the electoral system. It cites a lack of a reliable list of registered voters, insufficient candidate vetting and biased electoral organizations.
In some of the more volatile areas, locals claim the election is just a show so that Karzai can put a democratic label on a government that rarely answers to the people.
"The international community wants to say to the people: 'See in Afghanistan there is an election. There are posters and campaigning.' But the people are not so happy. They are too demoralized to go to the polling stations," said Mohammad Qasim Zazai, a carpet seller from eastern Paktia province.
"This regime of Karzai, it is symbolic, and so the election is symbolic. Most of the campaign workers are recruiting people from their villages. Fraud is continuing. People are buying these fake voter registration cards," Zazai said.
Printers in Pakistan say they have printed thousands of these fake registration cards. What remains to be seen is whether election workers will throw out these fake cards.
Complicating efforts to ensure a free and fair election, security has worsened in some areas since the polling station lists were first published last month.
Nearly 400 voting centers have been cut from the original list because Afghan forces could not guarantee security - a move that could lead to some of the same confusion about who should be voting where.
In one Taliban-heavy area of eastern Ghazni province, elders say they have been told that four of the five officially approved voting centers will not open.
"The district officials said to go to the main district center because the others won't be open," said Mahmoud, an elder from Shinkae village who like many Afghans goes by one name. Mahmoud is supposed to have a voting center in his village mosque, but the security forces said they couldn't secure it.
Despite the buildup of U.S. forces ordered by President Barack Obama, Afghanistan as a whole is less secure than at the time of last year's presidential election.
Although security has not worsened in the capital, Kabul, some northern provinces are less safe now and there's been no sign of significant improvements in the south and east.
There will be about 280,000 Afghan police and soldiers protecting the more than 5,500 voting centers scheduled to open on election day, according to Defense Ministry spokesman Gen. Mohammad Zahir Azimi.
Last year, there were about 150,000 Afghan forces protecting more than 6,000 voting centers. International forces will play a supporting role - at the ready to deal with attacks, provide medical evacuations and transport materials.
While campaign posters competed for space on building walls and electrical poles in the capital, many candidates did little campaigning in the provinces because of security concerns or the expense of hiring bodyguards for rallies or handshaking tours.
In eastern Paktia province and southern Kandahar province, candidates decided not to campaign at all because it was too dangerous, according to the Free and Fair Election Foundation of Afghanistan, the main Afghan observer body.
In many areas, the Taliban have threatened death to those who go to the polls - a very real danger given that the indelible ink used to keep people from voting multiple times can last for days.
In Shinkae, Mahmoud says the Taliban spread the word at mosque gatherings that anyone who votes will be killed. Mahmoud says he's unlikely to vote.
Other Afghans, though, see the vote as a chance to elect someone who could deliver roads, schools and other projects.
More than 2,500 candidates are vying for the 249 lower house seats. Afghan laws make it difficult to form political parties, so most candidates run as independents. The winners will serve a five-year term.
Preliminary results will be released as completed, with full preliminary results expected around Oct. 1. Final results are scheduled to be made public about Oct. 31, following resolution of complaints of fraud or misconduct.
Many observers worry that complaints from losing candidates could draw out the process, leaving parliament in limbo much as the presidency was for more than a month in 2009.