The tense arrangement was the result of a disastrous election season in 2008, when Mr. Tsvangirai won more votes than Mr. Mugabe in the first round of voting but refused to participate in a runoff because of state-sponsored attacks on his supporters. More than 200 people were killed.

This time, the vote was almost entirely free of violence, but the Zimbabwe Election Support Network, a coalition of local groups that observed the election, said the contest had nevertheless been marred by serious problems.

“We should not judge this election on the basis of peace and calm,” the group said. “There are other factors to take into account.”

It said that urban voters were significantly underrepresented on the contested voter rolls and disproportionately turned away at polling stations, a serious blow to the challengers because the Movement for Democratic Change’s support base is largely in Zimbabwe’s cities.

Much of the criticism centered on the list of registered voters, which was supposed to be made available in electronic form long before the day of the election so that candidates and observers could scrutinize it for ghost voters, duplicate registrations and other irregularities.

But the roll was given to the parties only the day before the election and on paper, making it almost impossible to analyze quickly. The vote had been rushed by Mr. Mugabe, who unilaterally declared that it must be held by the end of July, leaving little time or money to organize the election.