"It's like, oh, so you take half a salary and you do the same amount of work," said Michelle Obama. "They don't take anything off your plate. ... I was always guilty, 100 percent of the time. 'Am I doing my job to the fullest? Am I being the kind of mother I want to be to the fullest?'"
Michelle Obama, 44, breaks ground in other ways, White House historians say. She is the youngest first lady since Jacqueline Kennedy, who was 32 when she entered the White House in 1961.
Her children will be the youngest presidential pair since the Kennedy era, when Caroline, 3, and "John-John," born 16 days after his father's election, played hide-and-seek for photographers under their father's desk in the Oval Office. Amy Carter was 9 when she arrived in 1976.
On Monday, in a meeting with the first lady, Michelle Obama sought assurances that the White House could be "a home for a family," Anita McBride, Laura Bush's chief of staff, told ABC News.
"Mrs. Bush told Mrs. Obama that her little girls came here for the inauguration of their grandfather in 1989," said McBride. "The chief florist came and got the little girls, Barbara and Jenna, by the hand, took them up to the florist shop to make little flower arrangements that they can then have in their rooms while they were staying here."
In matters of style and grace, Michelle Obama has more often been compared to Jacqueline Kennedy, who had fewer political interests but equal star power.
Mrs. Kennedy proved that the image of the first lady can work wonders for foreign diplomacy, according to Letitia Baldridge, who served as her chief of staff from 1961-63.
"Jackie was the center of attention wherever she went," Baldridge told ABCNews.com. "When they made the state visit to France with President DeGaulle in Versailles, people in the streets were shouting 'Jackie, Jackie!' Kennedy might well have not gone."
Still, she said, "it's tough to be charming all the time. It takes a lot out of you to be gracious, and it's great that two people can share it."
Though the social responsibilities of being first lady have been apparent from the earliest days of the republic, the role has evolved.
Rosalynn Carter tried to reshape the office of first lady, taking a more assertive role in mental health and the child immunization policies by the end of her husband's presidency. But President Carter was widely criticized for his wife's initiative, especially when she visited Latin America in 1977 on the president's behalf.
Some wives became major players in their husbands' administrations. In 1986, a major newspaper described Nancy Reagan as having achieved something like an "associate presidency"; in 1993, one magazine outlined a first lady's accomplishments in an article titled "One Hundred Days of Hillary."
"People expect the first lady to be busy but not hovering over policy," said Edward Berkowitz, a professor of the history of the modern American presidency at the George Washington University.
Michelle Obama "won't do the nuts and bolts like Hillary and certainly not whisper in the president's ear like Nancy did to Ronald Reagan," he told ABCNews.com.
Michelle Obama has said she will be in the East Wind, not the West. She will have an office and a budget, but won't be paid. "The public still thinks that's appropriate," he said.