Mrs. Obama thought for a moment. Visiting so many living rooms had given her some new decorating ideas, she allowed.

Eight years later, the once reluctant campaigner is at the center of a multimedia charm offensive that may be the most closely managed spousal rollout in presidential campaign history. On Monday night, Mrs. Obama delivered a prime-time speech at the Democratic National Convention, preceded by an intricately made biographical video, a touch usually afforded to candidates, not their wives.

A relative newcomer to campaigning and the first black woman with a serious shot at first ladyhood, Mrs. Obama is a softer, smoother presence on the trail than she was at the start of the race.

Her basic message — the stirring life story, the full-throated advocacy for her husband, the maternal warmth — has remained constant. But instead of laying down challenges to her audiences, she solicits their concerns and showers them with empathy. She used to appear on news programs; now she gives interviews to “The View” and Ladies’ Home Journal. On Monday night she wore a designer dress, but lately she has more often sported a cheap-chic approach to fashion that might be called the economic crisis look: fewer designer pieces, more $79 Gap sundresses.

Now, in Denver and for the next 10 weeks, Mrs. Obama’s agenda is a double one. She must continue to refashion her own occasionally harsh public image in warmer tones. But that is only one of the two life stories she must sell to voters. Worried that Mr. Obama’s far-flung upbringing and his lack of deep roots leave some voters unsure and untrusting, the campaign is essentially substituting Mrs. Obama’s family background for his own.

Mr. Obama has few family members who can serve as surrogates. Just last week, a European magazine located one of the Kenyan half-siblings he barely knows, living destitute in a shanty. (The Texas Republican Party promptly turned the news into an attack ad.)

So on Monday night, the campaign filled the stage and screen with Mrs. Obama’s family: her basketball-coach brother, Craig Robinson; her homemaker-turned-secretary mother, Marian; and the memory of her father, Frasier, a city worker stricken with multiple sclerosis. (When her father was alive, the family barely talked about his disease, Craig Robinson said in an interview last year; now Mrs. Obama mentions it at nearly every campaign stop.)

Like the most famous of reassuring biographical videos, Bill Clinton’s “The Man From Hope,” Mrs. Obama’s film, “South Side Girl,” roots her in a specific, vivid place, the South Side of Chicago. As her mother tells Mrs. Obama’s story in a voice wavering with age, pictures of Mrs. Obama flash across the screen: as a child with pigtails, big brown eyes and an Easter basket, then as an adult with a child running into her arms.

Mrs. Obama’s presentation touched just a bit on her own career, as a lawyer, community organizer and hospital executive, concentrating instead on her roles as a daughter, a mother, a sister and a wife.

Mr. Obama is “the same man who drove me and our new baby daughter home from the hospital 10 years ago this summer,” she said in her speech, describing him “inching along at a snail’s pace, peering anxiously at us in the rearview mirror, feeling the whole weight of her future in his hands.”

Since she left her job as a hospital administrator to campaign and care for her daughters, Malia and Sasha, full time, some feminist critics have complained that Mrs. Obama sacrificed her own work for her husband’s. But from the very start, the Obama marriage was a kind of professional symbiosis, a partnership between two passionately ambitious people who found they could rise higher in the world together than alone.

The two Harvard-educated lawyers met at a law firm where she was assigned to guide Mr. Obama, a summer associate. From there, they tag-teamed their way through Chicago, sharing mentors, organizational ties and interests.

Mr. Obama turned his wife into a community organizer, and she eventually worked for some of his associates. Mrs. Obama, in turn, introduced him to some of the ambitious young African-American businessmen and civic leaders who would help fuel his political rise. Now they have fully fused their careers into one enterprise that has taken them farther than ever before.

The evening of the Iowa caucuses, the Obamas, who wanted to be away from the television, gathered their closest friends at a seafood restaurant in a Des Moines mall, where Mrs. Obama stood to give a toast. Everyone in the room knew that she had never really wanted her husband in politics, that she had once resented his absences and had expressed severe reservations before he entered the presidential race.

But now she stood and gave a more private, tender version of her campaign speech, misting up as she talked about her husband and his candidacy. “Here’s to my husband, the man I love and the man I believe would be the best president,” she said, according to Sandra Matthews, a friend.

Just then, a campaign aide broke in with news: the television networks were calling the state for Obama. As the room erupted in jubilation, as friends hugged, ignored their entrees and knocked over wineglasses, friends say, Mrs. Obama simply looked stunned.