A confident Michelle Obama takes the stage

CHARLOTTE, N.C. — Four years ago, Michelle Obama was something of a reluctant would-be first lady. She was living what she described Tuesday as a life “filled with simple joys … Saturdays at soccer games, Sundays at Grandma’s house.�

A successful White House quest would change all that, in unimaginable ways. She worried, she said, about how the burdens of office would transform her husband and her marriage. She said she worried more about how her young daughters, Sasha and Malia, would fare.

“How would we keep them grounded under the glare of the national spotlight?� she told the audience at the Democratic National Convention in a well-received 25-minute speech that contrasted her old fears for her family with the conviction that her husband’s policies had made life better not only for her children but for everyone’s.

“Today,� Obama said, “I have none of those worries, no, from four years ago about whether Barack and I were doing what’s best for our girls. Because today, I know from experience that if I truly want to leave a better world for my daughters, and all our sons and daughters … then we must work like never before, and we must once again … stand together for the man we can trust to keep moving this great country forward, my husband, our president.�

Her famously toned arms and shoulders showcased in a halter-cut rose-colored dress, Obama seemed more confident than she was on the convention stage in Denver four years ago.

Then, she was introducing herself and her husband to the country, seeking to underscore the fact that though they came from vastly different backgrounds — she grew up in a blue-collar Chicago family; he was raised by his single mother and grandparents in Hawaii — they shared common American values.

This time around, the country knows the Obamas. Her job was to explain why the country still needs her husband in the Oval Office.

Though she did recap the salient parts of their histories — including a mention of the glass ceiling that his grandmother, a banker, bumped against when men she trained were promoted ahead of her — the first lady devoted much of her speech to her husband’s policy achievements, including the healthcare law and equal pay for women. Obliquely, she mentioned his commitment to abortion rights and same-sex marriage.

In some ways, her speech seemed a sly rebuke to Republican tenets of self-reliance and to the party’s presidential nominee, Mitt Romney, whose background as the affluent son of a well-connected family is at stark odds with the Obamas’ modest upbringings.

Her husband, she said, “believes that when you’ve worked hard, and done well, and walked through that doorway of opportunity … you do not slam it shut behind you. … You reach back, and you give other folks the same chances that helped you succeed.�

As for her husband’s values, she said: “He’s the same man who started his career by turning down high-paying jobs and instead working in struggling neighborhoods where a steel plant had shut down, fighting to rebuild those communities and get folks back to work. Because for Barack, success isn’t about how much money you make; it’s about the difference you make in people’s lives.�

Like Ann Romney, who reached out to women and Latinos on the day after her speech at the Republican National Convention in Tampa, Fla., Michelle Obama will spend Wednesday firing up important voting blocs.

She is scheduled to visit the DNC’s African American caucus and the Latino caucus at the Charlotte Convention Center. She will also be the featured speaker at a luncheon for the Human Rights Campaign, a gay rights group. On Thursday, she and Jill Biden will visit the women’s caucus and pack USO care packages for service members returning from overseas deployments.

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