The initial round of Egypt’s first free presidential election in modern history has delivered a stark choice for next month’s runoff: a conservative Islamist vs. a former air force commander with deep ties to the man whose ouster precipitated this week’s vote.

After a raucous campaign involving 13 contenders, preliminary results on Friday from state media showed that the field had been whittled to a pair of candidates who represent the heavyweight forces of Egyptian politics — the Muslim Brotherhood and the military.

The Brotherhood’s candidate, Mohammed Morsi, has vowed to impose broader application of Islamic law. Ahmed Shafiq, who served as prime minister before Hosni Mubarak was toppled from the presidency in the 2011 revolution, campaigned as a secular leader who will thwart the rise of political Islam and restore security.

The choice leaves a large section of Egyptian society feeling disenfranchised and stunned, particularly because neither finalist was regarded as a champion of last year’s popular revolt.

“You’ll have a lot of people staying away from the polls. It’s a potential fiasco and a possible confrontation,” said Hani Shukrallah, editor of the English-language Web site of the state-run newspaper al-Ahram

While none of the leading candidates was considered ideal for U.S. interests, the two finalists are in many ways the worst, said Marina Ottaway, a Middle East expert at the Carnegie Endowment for International Peace.

“Shafiq would spell trouble because there might be another upheaval. It would be seen by many as a return to the old regime, and the country would be very divided,” Ottaway said. “Morsi would also be seen as a problem in Washington — too much power for the Muslim Brotherhood, and again the country would be divided.”

The Muslim Brotherhood urged the nation on Friday to unite behind its candidate to defeat Shafiq, calling on other presidential candidates to endorse Morsi. A leading member of the Brotherhood’s Freedom and Justice Party, Essam el-Erian, said in a news conference that Egypt’s revolution was in “danger.”

During the campaign, Morsi appealed to the legion of pious voters who have come to depend on the Brotherhood’s extensive charity network and appreciate its religious outreach. Although Morsi is an uncharismatic candidate, the group’s prodigious electoral machinery propelled him to first place in the voting.

A win for Morsi in the second round — which was triggered because no candidate reached 50 percent — would give the Brotherhood a near-monopoly on the country’s newly democratic government, following its sweep of parliamentary elections late last year. Many Egyptians fear that an empowered Brotherhood would turn the nation into a hard-line Islamist state modeled on Saudi Arabia, and they express misgivings about the group’s commitment to democratic ideals.

One major question for Washington if Morsi wins is how the Brotherhood — which has existed as an opposition force for decades — will choose to govern.

“The entire strategic relationship with the U.S. is something the Brotherhood has spoken against for years,” said Steven Cook, a Middle East fellow at the Council on Foreign Relations. That strategic cooperation has encompassed military exchanges, intelligence sharing, Suez Canal access and airspace.

“It’s unclear given the rhetoric how much more difficult it will be to conduct that kind of relationship with a government under Morsi,” Cook said.

But a Shafiq victory could be just as problematic for U.S. policymakers.

“There may be a presumption among the Egyptian public at large that the U.S. wants the military to retain as much power in the new government as possible,” said Michele Dunne, an Egypt analyst at the Atlantic Council. “But it’s not so clear-cut. If you have Shafiq elected in a way that’s disputed and creates major problems, that’s not in the U.S. interest either.”

Shafiq unabashedly calls Mubarak a role model, and opponents fear that he would restore his former boss’s secular police state, in which a heavy-handed security apparatus oppressed Islamists and other dissidents. In an interview this week, he said he would “neutralize” Islamists if elected.

Shafiq has appealed to Egyptians who are weary of the toll the revolution has taken on the economy and concerned about rising insecurity. He appeared to have the backing of the nation’s ruling generals, as well as state media.

“A lot of Egyptians stayed home watching the news and didn’t take part in the revolution,” said Rania Galal, 29, who voted for Shafiq. “They called us the silent. We’re the ones who voted for Shafiq.”

On Friday, Shafiq’s campaign defended its candidate against allegations that he is anti-revolutionary and autocratic.

“He is capable of working by the principles of the revolution and capable to deliver its targets,” said Ahmad Sarhan, a spokesman for Shafiq.

For many Egyptians, the choice they will face in the June 16-17 runoff is grim.

“We’re trapped between a fundamentalist and a killer,” said Fatma Emam, a feminist activist. “I’m very sad to say that the civilian revolutionary groups failed.”

Preliminary results showed a nation divided. The vote of Egyptians who felt passionately about the revolution appeared to have been split between progressive Islamist Abdel Moneim Aboul Fotouh and Arab Nationalist Hamdeen Sabbahi, the only major secular candidate who did not have ties to the Mubarak regime. Together, the two took nearly 40 percent of the vote, according to projections by al-Ahram’s Web site.

Morsi took about a quarter of the ballots, reflecting a drop in the Brotherhood’s popularity since it garnered just under half of the parliamentary votes. Shafiq received just under 24 percent.

Trailing badly was former Arab League chief Amr Moussa, a onetime front-runner, with about 10 percent of the vote.

In suburban Cairo, a few miles from the Brotherhood’s sparkling new headquarters, the excitement of Wednesday and Thursday’s balloting had worn off on Friday, and depression set in for many voters. Egyptians are known for their wit even during dark times. But voters interviewed on the streets of the Mokattam district conveyed nothing but gloom.

“It’s like we didn’t have a revolution,” said Ahmed Ibrahim, 27, a pharmacist and Aboul Fotouh supporter. “My fears of Shafiq are the same fears I had toward the old regime: oppression, crushing the opposition and the domination of one party over political life.”

Friends urged him to boycott the second round, but Ibrahim suggested that he will support Morsi. “I’m against the Muslim Brotherhood, but I will vote for anyone against Shafiq,” he said. “Boycotting would mean supporting Shafiq.”

Nearby, a 38-year-old clothing shop owner, May el Sherif, shook her head in disbelief.

“The choice between Shafiq and Morsi is bitter and painful,” she said. “We are choosing between two dictators — a secular, military one and a religious one.”

Mohamed Ashour listened to the preliminary results Friday and thought back to last year’s revolution. “This is not the Egypt we dreamed about during the cold days in Tahrir 15 months ago,” he mumbled, and walked away.

Special correspondents Haitham Mohamed and Ingy Hassieb in Cairo and staff writer William Wan in Washington contributed to this report.