Egyptians expressed wariness Saturday as they lined up in sweltering heat to vote in the runoff election for a replacement for ousted autocrat Hosni Mubarak.

In sharp contrast to recent elections, the mood in Cairo and across the country was largely tense as Egyptians contemplated the polarizing choice between Mohamed Morsi, a conservative Islamist, and Ahmed Shafiq, who was Mubarak’s last prime minister.

With the country’s lower house of parliament dissolved, the constitution suspended and the revolution pronounced all but dead, the outcome of the presidential vote that continues Sunday could not be more consequential.

“This is a decisive moment, but nobody feels confident about anything,” said Samia, 45, a Shafiq supporter who asked to be identified by her first name because of her government job. “It’s like rolling the dice and hoping for the best.”

The runoff began two days after a court ruling led to the dissolution of the lower house of Egypt’s Islamist-dominated parliament, a move that activists and some leading political figures described as a soft military coup. A small movement of boycotters urged voters to spoil their ballots in what they saw as an illegitimate election under military rule.

The once-repressed Muslim Brotherhood has thrived since the revolt that overthrew Mubarak. The group dominated the parliament and took a sizable share of the seats in a body tasked with writing a new constitution.

After the dissolution of the lower house of parliament this week, though, the military junta assumed all legislative powers. Military chiefs are soon expected to appoint a new constitutional assembly and issue a decree outlining the powers of the presidency.

That means the Brotherhood’s sole hope of remaining politically powerful in the short run lies with Morsi.

On Saturday, the Brotherhood appeared to be laying the groundwork to cry fraud if Shafiq is pronounced the winner. The group released a statement listing alleged violations, including military conscripts voting illegally and the arrest of revolutionaries holding pictures of slain protesters outside polling stations. However, the Brotherhood did not claim widespread fraud and expressed confidence that Morsi would win.

The group’s political wing had harsh words for Egypt’s military.

Dissolving parliament “confirms the desire of the military to take all authority against popular will,” a statement from the Brotherhood’s Freedom and Justice Party said. It said only a popular referendum could disband parliament. The statement called the move “an attack on the great Egyptian Revolution” and warned that the party would not honor the military’s decree about presidential powers.

“Egyptians, defend your will, continue to vote heavily,” the statement said. “Remember the blood of the martyrs and the pain of the injured and do not allow in any way the return of the tyrannical and despotic regime that has always despised the Egyptian people.”

Egypt’s transition has been marred by division among liberals, leftists and Islamists as well as what many see as the military rulers’ intention to protect their economic and political interests at the cost of democracy.

This week, the Justice Ministry effectively put the nation under martial law, authorizing the military police to arrest any citizen suspected of a wide range of crimes.

After voting in his home province of Sharqiya, Morsi promised a crowd of supporters, “I will lead you to the new Egypt and stability.”

“With our soul, with our blood, we’re with you, Morsi,” men chanted, thronging around the black sport-utility vehicle that carried the candidate.

In contrast, Shafiq slipped in through a side door of his polling station in suburban Cairo. The school was sealed off while he voted, and the former prime minister left with little fanfare.

Turnout appeared high in some parts of the country but relatively low in the capital. Polling stations opened at 8 a.m., and some Egyptians waited more than an hour to slip their ballots into plastic bins. Final results are expected Thursday.

About 150,000 security officers guarded polling stations across the country.

The balloting comes about 16 months after millions of Egyptians revolted against Mubarak’s repressive rule. But since his ouster, many here have grown weary of unending protests, flashes of violence and a faltering economy.

In Cairo’s working-class neighborhood of Imbaba, veiled women lined up outside a schoolhouse.

“Before, everyone was happy,” said Fatima Soliman, 50. “Now nobody is happy.”

When asked who she would vote for, she scanned the crowd warily and whispered, “Shafiq.”

To the north, “No to Shafiq” was scrawled in black paint at a school being used as a polling station in the suburban Cairo neighborhood of Shubra el-Kheima. Inside, voters trickled in under the watchful eye of military officers.

Morsi Ismail, 70, said he was thrilled that parliament had been disbanded.

The Brotherhood, he said, “was trying to control all our institutions.”

Rudji Mohamed, a 39-year-old upholstery repairman, was unwilling to say who he voted for but made it clear he was disheartened by the dissolution of parliament.

“We lived under repression for 30 years,” he said.

Special correspondents Hassan el Naggar and Ingy Hassieb contributed to this report.