The country faces what could be its first peaceful, democratic transfer of power as President Joseph Kabila, who took office in 2001, steps aside. Some observers, however, fear further unrest. The election commission chief has worried openly about rebels shooting voters waiting at the polls.
With political activities banned in the capital, Kinshasa, in the final days, residents instead gathered at newsstands to fiercely debate the fate of a country wealthy in minerals crucial for the world's smartphones and electric cars and yet desperately underdeveloped.
With the top candidates largely unknown until months ago, there is much to discuss.
Kinshasa's governor banned political activities in the vibrant opposition stronghold as leading candidate Martin Fayulu arrived to campaign. Fayulu, a businessman and Kinshasa lawmaker who emerged to lead an opposition coalition, has blamed Kabila's supporters for attempts to impede his campaign, including blocked flights and deadly assaults on supporters. Kabila has dismissed such accusations.
"The international community has to ask why only one candidate was disturbed," Fayulu told The Associated Press this week.
The opposition is fractured after Felix Tshisekedi, son of late opposition icon Etienne Tshisekedi, dropped out of the coalition to run on his own. Two other opposition heavyweights, former vice president Jean-Pierre Bemba and former governor Moise Katumbi, were blocked from running.
Even if the opposition were unified, some Congolese said it would have no chance against Kabila's preferred successor , ruling party loyalist Emmanuel Ramazani Shadary. His campaign billboards far outnumber those of other candidates in Kinshasa, but he is largely unpopular there.
Shadary is under European Union sanctions for obstructing Congo's electoral process as interior minister and for a crackdown on people protesting the election delay. The international pressure has annoyed Congo's government, and EU and other Western election observers have not been invited to watch Sunday's vote.
"No one loves the ruling party candidate but we already know what is going to happen. Sunday's vote is not credible and we will contest the results," said Ange Mvouessa, a civil servant who said he has not been paid in 18 months. He is backing Fayulu.
More than anything, he and others said they want peace in a country that has seen little of it.
Millions of people have died over two decades of fighting that began with the ouster of longtime leader Mobutu Sese Seko by a rebel coalition led by Kabila's father. Dozens of rebel groups remain active in the mineral-rich east and elsewhere.
Meanwhile, corruption is widespread. "Congo is a blessed country, we have everything but we are starving because of bad management," another Kinshasa resident, Thomas Basele, said. "We don't want corruption anymore, we are suffocating but Kabila doesn't want the population to speak," added Sylvie Imela.
The frustration flared into sometimes deadly protests as the election, once set for late 2016, was repeatedly delayed. Now the electoral commission's last-minute decision to bar some 1 million people from voting on Sunday because of an Ebola outbreak has brought more unrest.
Voters in the Ebola-hit cities of Beni and Butembo, where Fayulu campaigned to enthusiastic crowds, have protested. Health officials have said precautions were in place to allow the vote. The World Health Organization on Friday warned that "prolonged insecurity" could hurt what has become the second-deadliest Ebola outbreak in history.
The electoral commission is "manipulating the population to spark an uprising," Mvouessa, the civil servant, said. "But we know better than those manipulations. Congolese people don't want violence anymore."
Fayulu's opposition coalition has called for calm. Beni's civil society has urged residents to turn out again on Sunday and demand to vote with the rest of the country.
Congo's 40 million voters now face an unprecedented test. Voting machines are being used for the first time, bringing opposition concerns that they could be used to manipulate election results.
Critics say many in rural Congo have little or no computer experience, while officials project that each person should take under a minute to vote. Lack of electricity in large parts of the country could turn a malfunction into a mess. Some machines have to be carried on the heads of porters through the bush to reach remote polling stations.
Some Congolese election observers in the past week alleged that voting materials were not yet in place. In Kinshasa, a fire several days ago destroyed thousands of the machines and officials replaced most of them. Now people must use a limited number of polling stations.
The electoral commission says everything is ready, to shouts of disbelief.
"One thing is for sure, (the commission) is not playing transparency at all," said Luc Lutala, spokesman for one observer group, SYMOCEL. "We see trucks coming in and out from voting centers, but there is no way to know what is in it, or not."
Less than 48 hours before the vote, police in Kinshasa guarded newly delivered equipment at polling stations. But several people trained to be electoral agents told the AP they had yet to see a voting machine.
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