Cairo (CNN) -- The presidential runoff election in Egypt this weekend pits an Islamist against a symbol of Egypt's former dictatorial regime: the Muslim Brotherhood's Mohamed Morsi and former Prime Minister Ahmed Shafik.
And there was a third option as polling began Saturday: boycott.
The stakes are high -- the future of Egypt's hard-won revolution rests in ballots cast this weekend amid political chaos. Egypt has no constitution and now, after a shocking court ruling, no parliament. It was declared invalid Thursday and dissolved Friday.
The Muslim Brotherhood rejected Saturday the dissolution of parliament as a dangerous step taken by the military and called for another referendum on the matter.
"We are calling for a referendum again on the dissolving of parliament and see it as the logical thing to do especially after 30 million people went to the polls the first time and the country spent over 3 billion Egyptian pounds in a transparent electoral process," said Mahmoud Ghozlan, spokesman for the Brotherhood.
Many Egyptians have expressed fears that their revolution is unraveling; that the military, long the central nerve system of Egypt, will never relinquish power.
"I was planning to boycott the elections because I feel neither candidate represents the Egypt we wanted, but my family convinced me," said Yousef Hamad, a retired English professor in central Cairo, who would not reveal how he voted.
"These next two days will shape Egypt's history," he said. "I am standing in the long line to vote for the more experienced candidate who will hopefully save Egypt's economy before it completely collapses."
The polls opened at 8 a.m. Saturday. Farouk Sultan, head of Egypt's Presidential Election Committee, announced that polling hours were extended by an hour to 9 p.m. The polls open again Sunday morning and remain open until 8 p.m. Votes must be counted by Monday, with final results expected Thursday.
The heat kept turnout relatively low much of Saturday, but voting picked up later.
Officials reported few voting irregularities, Sultan said.
The April 6 youth movement, behind many of the protests in Tahrir Square last year, said three dozen members were arrested, most later being released.
"The new martial law seems to be in full effect," said spokesman Hisham Mohamed. "They are obviously targeting us and we think it will get worse if Shafik is president."
Although the political situation has been difficult, U.S. Rep. David Dreier, R-California, an observer, said the election is significant.
"For the first time in 7,000 years the people of Egypt this weekend are going to elect a president and no one knows for sure who the winner is going to be," Dreier told CNN. "I think that is an accomplishment."
The excitement of being able to choose a candidate could not be underestimated. But that choice, for some, came down to the lesser of two evils.
Farouq Magdy supported Hamdeen Sabahy, a candidate who didn't make the runoff. Now, after the constitutional court's ruling and the recent release of six former Interior Ministry officials, he felt the military council was asserting its authority.
That's why Morsi, he said, was "the better of two choices."
But hotel manager Mohammed Ali said a majority of his staff was voting for Shafik.
"We need security and we want to recover economically," Ali said. "Not because Shafik is a great option, but let's say he is the best of the worst."
Or consider these two differing opinions:
"I do not trust anyone with a beard. So I am voting for Shafik," said fast-food shopkeeper Kamaal. That's a reference to Morsi, a conservative Muslim with a beard.
But jeweler Mohammed Ahmed recalled Shafik say on television last year that he would personally guarantee the safety of protesters at Tahrir Square. When it didn't happen, the least he should have done was resign, Ahmed said.
"I am voting for Morsi because I feel Shafik has betrayed Egyptians last year when he was Mubarak's prime minister," he said.
The runoff follows a May election that failed to produce a winner with a clear majority.
No one knows how much power Egypt's new president will wield. A constitution that will define his role has yet to be drafted and a new round of parliamentary elections has not yet been scheduled.
But one thing is clear. Morsi or Shafik will report directly to Egypt's Supreme Council of the Armed Forces, the powerful military leaders who have been ruling Egypt de facto since Mubarak's departure.
Some disgruntled voters launched a campaign to invalidate ballots, said Mohamed Ghoneim, the founder of a group that marked X on the names of both Morsi and Shafiq, thereby nullifying their vote.
Political scientist Amr Hamzawy wrote a newspaper article on the boycott.
"There are different kinds of political and psychological blackmail taking place these days against citizens who have already made up their mind and decided to boycott the presidential runoff elections," he wrote.
"I register my intention to revoke my vote by refraining from voting for any of the rival candidates, and also place on record my respect for the rules of electoral competition and I will respect the result as long as the electoral process was characterized by integrity, and absence of fraud."
Among the boycotters was Mohamed Khamees, who handed out leaflets.
Khamees said he lost sight in his left eye from a police beating in Tahrir Square during the early 2011 protests.
"If I give this country for the Brotherhood hands, there is not going to be any more Egypt, it will be destroyed," he told CNN. "And if I give it to someone from the old system, it looks like we did nothing."
Prominent journalist Bilal Fadl attacked Muslim Brotherhood members for months for an alleged lack of performance in the parliament they dominated. But now, he has changed his mind.
"Do you still think it is better to give your voice to Ahmed Shafik so he can become the first Egyptian president since the revolution?" Fadl wrote.
"That's the revolution for which hundreds sacrificed their lives ... under the political responsibility of Shafik. Would you give your voice to someone who got his legitimacy from his being anti-revolution or give it to someone who is pro-revolution but only differs with you (in approach)?"
These are questions pondered by 50 million eligible voters this weekend.
Businessman Hussain Mahmoud voted for Morsi. Hussein doesn't want soldiers, serving or retired, to lead Egypt.
"They consider themselves superior to other human beings," he told CNN. "They're used to giving orders and those below carrying them without discussion."
Mahmoud was interrupted by Mabrouk Mikhail, a Coptic Christian, former army officer and supporter of Shafik. He insisted religion must stay out of politics.
"Frankly, the Brotherhood failed in parliament. They were a farce and nothing good came of them," Mikhail said.
Despite tensions, Saturday's polling was mostly calm, said Gen. Mohsen Mourad, head of security in Cairo.
The Supreme Presidential Electoral Commission has approved licenses for 53 organizations to observe the elections, including at least three international groups -- the U.S.-based Carter Center, the South Africa-based Electoral Institute for Sustainable Democracy in Africa and the Arab Network for Monitoring of Elections.
CNN's Amir Ahmed, Saad Abedine, Moni Basu, Ivan Watson, Mohamed Fadel Fahmy, Ben Wedeman and Faith Karimi contributed to this report.