CAIRO, Egypt —

He doesn't inspire and few would call him charming, but Mohammed Morsi is within reach of fulfilling the Muslim Brotherhood's 84-year-old dream of imposing political Islam on an Egypt that for generations has been dominated by harsh colonial and secular masters.

The 60-year-old presidential candidate speaks of inclusion even as ultraconservative clerics herald him as the leader of a new Islamic caliphate. He has reached out to Egyptians with a kaleidoscope of unpolished sound bites — while calling Israelis "killers" and "vampires" — but the Brotherhood's opaque nature has masked Morsi's deeper political intentions if he and his fellow Islamists control the government.

The two-day election runoff beginning Saturday between Morsi and Ahmed Shafiq remains too close to call. But when votes are counted, Morsi, a stocky, Islamic conservative with a trimmed beard, will learn if this agitated country has agreed to enter an uncertain new era or return to the grip of the past.

Egyptians face the starkest of choices after 16 months of unrest. A slight plurality of voters in the first round of presidential balloting supported liberal, socialist or moderate Islamic candidates. They now must choose between Shafiq, who many deplore as an echo from a repressive regime, and Morsi, who many liberal activists believe will curtail civil liberties for women, Christians and other non-Muslims.

The central question: Would Morsi bring forth a brash, entrepreneurial Islamic democracy like Turkey's or gravitate toward the fundamentalism of Saudi Arabia and other Persian Gulf states? Either way, Egypt, long the cultural center of the Arab world, will influence governments rising from the rebellions that have swept the Middle East and North Africa.

For many, a vote for Morsi is less an embrace of the Brotherhood than a condemnation of Shafiq. The secular April 6 Youth Movement, at the forefront of last year's uprising that toppled Hosni Mubarak, announced this week it is backing Morsi for that reason.

"I endorse Morsi without a doubt," said Ahmad Nabil, a liberal activist. "If Shafiq comes, he'll bring back the entire old regime. This does not mean I'm not fully convinced of Morsi, but I don't want to give Shafiq any legitimacy."

Morsi wasn't the one the Brotherhood wanted representing it at this seminal moment. Its first presidential candidate was Khairat el-Shater, a wealthy businessman who spent years in Mubarak's prisons and was the group's key strategist. The election commission disqualified him over his criminal past, and Morsi, who quickly became known as the spare tire, accepted the mantle of the nation's best-organized political machine.

Morsi, who earned his doctorate in engineering at the University of Southern California, was the disciplinary and often unseen hand in the Brotherhood's leadership. His goal is to revive Egypt's economy and return the country to prominence.

"The presidency will not be reduced to one person," he said. "The age of superman has failed and gone. The world is no longer like that. I am not like that."

Morsi was arrested during the revolt against Mubarak, but he is regarded by liberals as less an embodiment for change than an Islamist who will emphasize religion at the expense of the country's deep social and financial problems. He and the Brotherhood often are seen as chameleons, pretending to speak for the revolution while advancing their political agenda in quiet deals with Egypt's military rulers.

Several liberal parties this week boycotted negotiations on naming a panel to draft a constitution over accusations that Islamists were maneuvering for control. A leading Egyptian judge has suggested the judiciary, which monitors elections, may put aside its impartiality to stop a Brotherhood that wants to "destroy this country."

This is not "the time for Morsi," said Nour Eldin, who stood in Tahrir Square recently. "The Brotherhood is too closed, and they make decisions without consulting the people. If they come to power, they will divide Egyptians. We don't need that now."

Morsi's campaign headquarters is surrounded by barricaded streets, a testament to Egypt's reshaped political terrain and fresh ironies. The villa sits across from the Ministry of Interior, which for decades jailed and tortured thousands of Brotherhood members. The juxtaposition speaks less to harmony than to a hint of battles to come.

After decades of running nationwide religious and social programs, including clinics and schools, the Brotherhood's time has come to occupy the presidential palace, said Tarek Farhat, a Morsi spokesman.

"We need to finish, and the revolution must continue," Farhat said. "We need the people just to give us our chance. If we fail, they can kick us out in four years."