CAIRO — Naglaa Ali Mahmoud wears an Islamic head covering that drapes down to her knees, did not attend college and never took her husband’s last name, because that is a Western convention that few Egyptians follow. She also refuses the title of first lady, in favor of simply Um Ahmed, a traditional nickname that identifies her as the mother of Ahmed, her eldest son.

Egypt has a new leader, Mohamed Morsi, the first president to hail from the Muslim Brotherhood. And it also has Ms. Mahmoud, 50, whose profile is so ordinary by contemporary Egyptian standards as to make her elevation extraordinary. Ms. Mahmoud could hardly be more different from her predecessors, Suzanne Mubarak and Jihan el-Sadat: aloof, half-British fashion plates with well-coiffed hair and advanced degrees.

With her image as a traditionalist everywoman, Ms. Mahmoud has come to symbolize the dividing line in the culture war that has made unity an elusive goal since the ouster of Hosni Mubarak. For some, she represents the democratic change that the revolution promised. She is a woman in the presidential palace who looks and lives like their sisters and mothers.

But to some in the westernized elite, she stands for a backwardness and provincialism that they fear from the Islamists of the Muslim Brotherhood.

“I can’t call her a first lady under any circumstances,” complained Ahmed Salah, 29, a banker having coffee with his friends on the Nile island of Zamalek. “She can’t be an image for the ‘ladies’ of Egypt.”

Her image has become the subject of a rancorous debate on Web sites and in newspapers. A column in the newspaper El Fagr asked incredulously: How could she receive world leaders and still adhere to her traditional Islamic standards of modesty? “Don’t look at her. Don’t shake hands with her,” the paper suggested, calling it a “comic scenario.”

Noran Noaman, 21, an engineering student, said Ms. Mahmoud embarrassed her. “If you travel to New York or wherever, people would make fun of you and say: ‘Your first lady wears the abaya, hahaha,’ ” she said. “Previous first ladies used to be elegant.”

Many others, though, said it was her critics who were out of step. “People like Suzanne Mubarak are the odd ones out — you don’t see them walking down the street,” said Mariam Morad, 20, a psychology student. “This is exactly what we need: change.”

Dalia Saber, 36, an engineering lecturer, said, “She looks like my mother, she looks like my husband’s mother, she probably looks like your mother and everybody else’s.”

For her, Mr. Morsi and Ms. Mahmoud were what the Arab Spring was all about: regular people in power.

“They’re people like us,” she said. “It is a strange relief to people. The people feel that there’s a change.”

Ms. Mahmoud, for her part, said she knew it would not be easy to be the wife of the first Islamist head of state, as she told the newspaper of the Muslim Brotherhood, the 84-year-old Islamist movement. If she tries to play an active role, she risks comparisons with Mrs. Mubarak, who was widely despised for her supposed influence behind the scenes. But if Ms. Mahmoud disappears, she said, “They will say that Mohamed Morsi is hiding his wife because this is how Islamists think.”

Ms. Mahmoud’s unexpected path to the presidential palace illustrates just how foreign her experience is to the culture of the old Egyptian elite — or perhaps how foreign that elite is to Egypt. Hers was a very typical beginning: She grew up in the poor Cairo neighborhood of Ain Shams, and was 17 and still in high school when she married her cousin, Mr. Morsi, who was 11 years older. He also had grown up poor, in the small village of El Adwa in the Nile Delta province of Sharqiya, but excelled in the engineering program at Cairo University.

Three days after their wedding, he left for Los Angeles, to complete his Ph.D. at the University of Southern California. She finished high school and studied English in Cairo. A year and a half after their wedding she joined her husband in Los Angeles, where she volunteered at the Muslim Student House, translating sermons for women interested in converting to Islam.

It was in Los Angeles that she and her husband were first invited to join the Muslim Brotherhood, an offer that would later define their lives. “I always say that the Brothers don’t blindfold anyone,” she told the group’s newspaper. “From the beginning they told us about the situation and what was asked of us, and they told us that the path is long and full of dangers.”

She said the Brotherhood recruiters told Mr. Morsi to be sure his wife approved of the decision before joining, telling him, “We care about the stability of the family more than having one more member.”

The first two of their five children were born in Los Angeles and hold American citizenship. After Mr. Morsi completed his degree, Ms. Mahmoud initially did not want to leave Los Angeles, she said in an interview with a Brotherhood Web site. But Mr. Morsi wanted his children to grow up in Egypt.

After they returned, in 1985, Mr. Morsi taught engineering at Zagazig University near his hometown north of Cairo in the delta and began a climb through the Brotherhood’s ranks. Ms. Mahmoud, a homemaker, became an instructor in its parallel women’s auxiliary, teaching young girls about marriage. “Men are designed to lead and women to follow,” the group’s curriculums explain.

Like many Egyptians, he traveled abroad to earn extra income, teaching engineering at a Libyan university from 1988 to 1992. He finally made enough money to leave their small rented flat and buy an apartment in Zagazig and make a down payment on a Mitsubishi Lancer sedan, family friends back in Sharqiya said.

The Brotherhood was an outlawed movement under Mr. Mubarak, and playing a role in its leadership was not always easy for Mr. Morsi or his family. “I don’t know if I will come back to see you,” he told her before he left for a protest in 2006. “The next time we meet could be in Tora Prison.”

He did not come home for about seven months, which he spent in detention, Ms. Mahmoud told the Brotherhood newspaper.

Among her sons, Ahmed was detained several times, Osama was detained and beaten during last year’s revolt, and Omar was also assaulted. (Like his father before him, Ahmed is working abroad to make money, as a urologist in Saudi Arabia.)

In 2000, Mr. Morsi was elected to Parliament, becoming the leader of the Brotherhood’s bloc of 17 lawmakers, but lost in the next election amid charges of widespread fraud by Mr. Mubarak’s governing party.

In Egypt’s patriarchal culture, and especially among Islamists, men seldom talk publicly of their wives, and mentioning them by name is almost a taboo. But Mr. Morsi is unusually appreciative of Ms. Mahmoud, even in public, sometimes saying in television interviews that marrying her was “the biggest personal achievement of my life.”

He sometimes helped her with chores, she told the magazine Nesf el Donia, and even cooked for her. “I like everything about him,” she said. “Our fights never lasted for more than a few minutes.”

She often appeared with her husband during the campaign, though she seldom spoke publicly. When a magazine journalist asked for a photograph, her answer was conditional. “Only if your photos make me look younger and a little thinner,” she said.

Now, Egyptians began to marvel and laugh at the thought of a small- town homemaker in the presidential palace. “Um Ahmed called Um Gamal,” some jokes begin, referring to Mrs. Mubarak by the name of her son Gamal.

Ms. Mahmoud, though, says she is not so sure about the palace: “All I want is to live in a simple place where I can perform my duties as a wife. A place like the presidential palace completely isolates you from the world people live in, and going too far hardens the heart.” (Copyright 2012 The New York Times Company 06/28/12)