Egypt's main opposition bloc on Sunday alleged widespread fraud and called for mass protests after preliminary results showed supporters of a controversial draft constitution winning a solid majority in the first round of balloting.
The call had the potential to throw Egypt back into disarray after several days of relative calm that included orderly voting Saturday by about 8 million citizens. Preliminary tallies by the Muslim Brotherhood and state media showed that 57 percent of voters backed the constitution, with a second round of voting still to come. Many of those who voted for the charter said they were doing so to restore stability to the country after nearly two years of tumult that began with a successful push to oust President Hosni Mubarak.
But in a Sunday night news conference, the opposition National Salvation Front alleged there had been thousands of complaints of voting irregularities that "went beyond the rigging that used to take place under the previous regime."
The group, a loose coalition of liberals, leftists and Christians that has emerged to challenge the ruling Islamists, called on Egyptians to protest Tuesday "in order to defend their free will and to prevent any rigging of their decisions."
The opposition's reaction to its apparent defeat seemed to end any hopes that the referendum might bring calm to Egypt after weeks of clashes over both the substance of the new constitution and the hurried way it was put before voters.
The unofficial results of the first round reflected a narrower-than-expected victory for the charter, which was strongly backed by President Mohamed Morsi and his allies in the Muslim Brotherhood. Wider margins are forecast Saturday during the second and final round of balloting, when voting shifts to smaller cities and more rural areas, where Islamists have a clear edge.
"The Egyptian people have expressed their free will," the Brotherhood's political arm said in a statement. The group's early vote tallies have proved accurate in past elections.
But opposition leaders quickly disputed the unofficial results, claiming that the referendum had actually been voted down by wide margins in the major cities of Cairo and Alexandria. Rights groups, meanwhile, said that the voting was inadequately monitored and that some people had been prevented from casting ballots. They called for a rerun of the referendum.
With Morsi staking his young government on the new charter, that was considered highly unlikely. In the weeks before the referendum, Morsi gave himself extraordinary powers as he maneuvered to bring the constitution to a vote. Resulting street clashes left at least 10 people dead and hundreds injured.
Although much of Egypt was calm Saturday during the vote, the unrest resumed overnight, with the liberal al-Wafd party saying that its offices had been attacked by a group of hard-line Islamists known as Salafists.
"The referendum has passed, but it doesn't mean the end of the divide in this country," said Gamal Soltan, a political science professor at the American University in Cairo. "The opposition may be demoralized in the short term, but the reasons for the anger are still there."
Opposition leader and former foreign minister Amr Moussa said in an interview that even if 57 percent of Egyptians voted in favor of the document, "it means there is no consensus on the constitution." Moussa said that a two-thirds majority should be required for such a critical vote but conceded that the opposition would have little choice but to accept the results if the projected margins hold.
Brotherhood supporters, meanwhile, were confident that their side had won and that with each successive victory at the ballot box, their vision for Egypt was coming to pass.
"Freedom for the seculars is different than freedom for the Islamists," said Ahmed Morad, a 40-year-old Brotherhood supporter. "The seculars call for the separation of religion and state. The Islamists are calling for the state and religion to be the same thing."
Egyptians disagree over whether that is where the constitution will lead. The document establishes Islamic law as the principal source of legislation, but so did the constitution that was in force throughout Mubarak's tenure.
The new charter includes provisions protecting the rights of Christians and Jews, and proclaims the people, not God, to be the source of all government authority. Many Salafists have expressed disappointment that the document does not go as far as they would like in promoting the role of religion in public life.
But secular opponents of the draft constitution say it is vague enough that legislators and judges can use it to restrict the rights of women and religious minorities. Non-Islamists pulled out of the constitution-writing process before it was complete, arguing that their views were not being taken into account.
If the constitution passes, the focus in Egypt would quickly shift to parliamentary elections, which must be held within two months. Islamists dominated the previous elections, held a year ago, the results of which were later annulled.
The opposition, which has been beset by division and disorganization, has only a small window to decide whether to continue to protest the constitution or focus on the parliamentary vote.
Opposition leaders have proved adept at bringing thousands to the streets to demonstrate, but they have been far less successful in attracting the millions of voters necessary to win at the ballot box.
At a time when many Egyptians appear to crave stability, a return to protests could be risky for a group that had been showing signs of greater political maturity.
"Even though they lost, they developed organizationally," Soltan said. "Whether they will be able to maintain that is an unanswered question."
Ingy Hassieb contributed to this report.