Dozens of Sudanese refugees were lined up on a street in Old Town Alexandria, poised to vote for the creation of a new nation from a cardboard booth 6,000 miles away. They sang. They danced. They shouted, “Oye south Sudan!”

But one of those in line, 26-year-old college student Nyater Ngouth, found herself seized with unexpected doubts. As the clamor built on Sunday — the first day of remote voting that will continue all week in Alexandria and seven other polling places in the United States — Ngouth stayed quiet.

“I started thinking, ‘Can I do this? What if this new country fails? Can I bear the responsibility?’ ” she said.

Like thousands of southern Sudanese living in the United States, Ngouth welcomed the chance to vote in the referendum on the region’s secession. For the overwhelming majority, secession offers a chance to move on from decades of civil war against a government controlled by northerners, including Sudan’s president, Omar Hassan al-Bashir.

Ngouth, tall and elegant with long brown hair, has plenty of private reasons to want independence. Sudan’s civil war had led to her father’s imprisonment and death in 1984. It forced her to flee from her village to Egypt as a young girl. She ended up in D.C. with her grandmother as a teenage political refu­gee, beginning evening classes at Roosevelt Senior High School in Northwest Washington, where she later graduated as valedictorian.

Ngouth now is a second-year biology major at the University of the District of Columbia. Yet Sudan’s volatile politics may change her life’s trajectory yet again. Ngouth has vowed to herself that if the referendum passes, she will return home. She could open a pharmacy, maybe, or a community health clinic.

But Ngouth, whose first name, Nyater, means “the girl born during conflict,” struggles to envision her home free and at peace. “What if this is all a mistake?” she asked herself as the line inched forward. “Maybe the risk is too great.”

The gravity of the Sudanese referendum is especially profound for those who fled the bloodshed as children, settling into lives in comparatively comfortable U.S. cities and suburbs, earning diplomas and degrees from American schools. Many say they now are preparing to leave all of that behind, to return to a region they hardly remember.

Votes from polling places around the world, including the eight in the United States, will be added to the several million expected in Sudan. In the United States, 9,000 people are expected to decide between secession, represented on the ballot by a drawing of a single open hand, and unity, represented by two clasped hands.

In Sudan, many people rely on such symbols: More than 75 percent of adults in southern Sudan cannot read. With such a poor education system, it’s not clear where the new country will find its next generation of leaders. Increasingly, it looks like they might be drawn from the diaspora, including the Washington area, which is home to several hundred southern Sudanese.

Refugees, many of them products of Washington-area schools, have returned to Iraq and Afghanistan in recent years to aid in reconstruction efforts in countries they left as children. Some have gone with American firms. Others have become part of nascent bureaucracies. Something similar may soon happen in southern Sudan.

“There’s a whole generation in southern Sudan that hasn’t been educated at all. The diaspora is seen as a critical constituency in looking to fill that gap,” said Richard Downie, deputy director and fellow of the Africa program and the Center for Strategic and International Studies, a Washington-based think thank.

On the same day that Ngouth wrestled with her vote, Nhial Agok, 19, a senior at James Hubert Blake High School in Silver Spring, arrived at the polls in Alexandria at 6 a.m. Yet he had none of her doubts. When his turn came, he ducked behind a plastic yellow curtain and marked the box next to the open hand.

“For a while, it was my father’s dream, not mine,” said Agok, 19, who fled Sudan when he was 5. “But now it’s something I want personally — to go back, to make things better.”

At Blake, Agok is an honor student and a track star who just cracked two minutes in the 800-meter run. In Sudan, where the number of educated leaders is limited, his American schooling could put him on the fast track to a prominent spot in southern Sudan’s business or political community.

Yet refugees from southern Sudan will face steep challenges if they return home. For the new nation, there will be a national government to build as well as questions of how to distribute oil revenues and how to fund infrastructure in a country that would become one of the world’s poorest states.

Those questions weighed heavily on Ngouth as she inched forward in line. Yet around her, the mood became increasingly celebratory, as voters flashed their identification cards and prepared to dip their thumbs into containers of blue ink — the same color used in dusty polling places across southern Sudan.

“I’d be surprised if a single person here is voting for unity,” said Angelos Agok, 42, a former soldier with the Sudan People’s Liberation Army and the father of Nhial Agok, as he stood in line. “We’re all for secession.”

But when Ngouth’s turn came, she tossed the yellow curtain over her head and, in privacy of the voting booth, paused to stare at the ballot, surprised by her own hesi­ta­tion. “I thought I was sure about this for so long,” she said afterward.

And then, in a rush of determination that came from some unknown place, she suddenly found conviction. Next to the single, open hand and the word “secession,” she pressed an inky thumb to the ballot.

“We cannot be certain that this will work perfectly,” Ngouth said after emerging. “But we can be sure that it is the right thing to do, and that there is a future for a new Sudan.”