The low participation could reflect voter fatigue. Since Mubarak's fall, Egypt has held a referendum on initial, transitional constitutional amendments and votes for the two houses of parliament and for the president, which each had run-off rounds — and now the current referendum.
But pollster Magued Osman, head of the independent Egyptian Center for Public Opinion Research, said that shouldn't have been the case in Cairo and Alexandria — the country's two biggest cities — since they "have been key in the debate over the constitution."
Of Cairo's 6 million registered voters, only 2.1 million voted, down from 3.6 in the presidential runoff in June, he said.
He and other experts said one factor could have been skepticism about the integrity of the vote after most judges, in a protest against Morsi, refused to oversee the referendum, as is customary in Egypt.
Along with the shortage of monitoring judges, the short time to prepare for the vote — Morsi announced the referendum's date on Dec. 1 — led to chaos in most polling centers.
Many of the judges who agreed to oversee the vote were loyal to the president and his Brotherhood. Activists have accused them of looking the other way while violations marred the vote.
Some accused pro-Brotherhood authorities of trying to suppress the "no" vote. In some opposition districts of Cairo and Alexandria, voters had to wait in line for up to 10 hours, with some leaving in frustration before casting their ballots.
"It is not so far-fetched to believe that stalling was responsible in part for the low turnout as part of a tactic adopted by the Islamist supporters of the constitution," Sabry told The Associated Press.
Judges in charge of polling centers, voters said, took long breaks to eat or pray. Some picked fights with voters who demanded they show documents proving they are indeed judges. Many polling centers closed at 7 p.m., ignoring the election commission's decision to extend voting until 11 p.m.
"Many of the judges closed early on the pretext that they had not received written instructions to extend voting," said Negad Borai, a prominent lawyer and rights activist. "All the problems surrounding the referendum could have been solved if Morsi seriously sought consensus on the draft, rather than ram it through."
Others stayed away in a deliberate boycott of what they called a flawed system manipulated by Islamists.
"The lines were very long. The atmosphere was unsafe," said Nayrouz Abouzid, a 32-year-old magazine publisher and head of a PR firm in Cairo. "Additionally, I felt that by voting I would be legitimizing a process that is both absurd and ridiculous."
Tarek Shalaby, a blogger and a veteran of the anti-Mubarak uprising, pointed to the Constituent Assembly that approved the draft, saying it was not representative.
"If the process of drafting the constitution was appropriate, but the outcome was bad, I would have taken part and said 'no'," he said. "I will not allow them to take me to their court to play their game."