Michelle Obama will try to do more than introduce herself as a potential first lady Monday night when she takes the stage at the Democratic National Convention in front of a nationwide TV audience.

The setting gives her an opportunity to reinvent herself after being portrayed by Republicans as unpatriotic for saying during the primaries that her husband's campaign made her proud of America "for the first time."

"She has been by all accounts a polarizing figure in this campaign," NPR Correspondent Juan Williams said Monday. Williams, a FOX News contributor, said the "proud" comment defined her for a lot of voters.

"It's off-putting to a lot of people, but especially to middle-of-the-road white America," Williams said. "So tonight she wants to reinvent herself. She wants to say, 'Hey, listen, that's a distortion, a caricature of who I really am.'"

The wife of the presumptive Democratic presidential nominee will be introduced by her older brother, Craig Robinson, who is head basketball coach at Oregon State.

According to excerpts released before her speech, Obama is to talk about her and her husband's life together and their building a family grounded in faith and values.

"I come here as a wife who loves my husband and believes he will be an extraordinary president. I come here as a Mom whose girls are the heart of my heart and the center of my world - theyre the first thing I think about when I wake up in the morning, and the last thing I think about when I go to bed at night. Their future -- and all our childrens future -- is my stake in this election," she is to say.

"And in the end, after all thats happened these past 19 months, the Barack Obama I know today is the same man I fell in love with 19 years ago. Hes the same man who drove me and our new baby daughter home from the hospital ten years ago this summer, inching along at a snails pace, peering anxiously at us in the rearview mirror, feeling the whole weight of her future in his hands, determined to give her everything hed struggled so hard for himself, determined to give her what he never had: the affirming embrace of a fathers love," she will say.

Michelle LaVaughn Robinson grew up on the South Side of Chicago in a family of modest means. She fought her way into Princeton, and later to Harvard Law School, and began dating Obama while working at a corporate law firm in Chicago. They've been married for 15 years.

In the primaries, she was dubbed "the closer" for her ability to persuade undecided voters to come on board. Now she's the opener, the first-night star called upon to testify about her husband's vision and values.

Like any candidate's spouse, she is in the unique position of knowing the candidate best. Barack Obama has made no secret of how much he values his wife's insight.

Asked by pastor Rick Warren at a forum last week whom he'd rely on most for advice in his administration, Obama said: "That’s Michelle, my wife, who is not only wise, but she’s honest. And one of the things you need ... is somebody who can get up in your face and say, 'boy, you really screwed that one up'."

Not everyone is so trusting.

To a large extent, Michelle Obama faces a task that no other potential first lady has: She must reassure voters that she loves her country. Obama has said that her statement about being proud of America for the first time referred to having pride in the political process.

But the critics have not let up, to a point where her husband told people to "lay off my wife," and the Obama campaign created a Web site solely to counter innuendo about both of them.

A summer AP-Yahoo News poll found the public hasn't taken to her yet. Respondents were more apt to dislike her than Republican candidate John McCain's wife, Cindy. But polls also show that Americans don't know either woman well.

For many voters, her speech Monday night will be her debut on the public stage. While she has campaigned solo for her husband, some of the heaviest TV coverage she has received has been the Republican videos criticizing her "proud" remarks.

Michael Steele, former Republican lieutenant governor of Maryland, said Michelle Obama alone is responsible for her image, and that her speech is a chance to counter that.

"I think what she wants to accomplish is to show America that she's a mom, she's a wife, she's a businesswoman ... and that she is capable of being the first lady of this country," Steele said. "And her challenge tonight is to do that in the context of perceptions, real or imagined, that Americans have of her. Some would say militant, some would say anti-American."

Democratic strategist Chris Kofinis said he thinks Obama will be able to express her personal story of accomplishment as well as a full picture of what she and her husband are fighting for and why.

But Kirsten Powers, a FOX News political analyst, said Michelle Obama should not talk too much about herself.

"Michelle Obama really needs to connect with ordinary people and she needs to promote her husband, not herself," Powers said.

Mrs. Obama did a walk-through at the Pepsi Center Monday afternoon with daughters Malia, 10, and Sasha, 7. Both girls stood at the podium and practiced pounding the gavel.

Williams said Obama's race is playing a big factor in the way she's being portrayed.

"I think it's also a factor that she's an educated professional black woman," he said. "It's as if you're adding multipliers to this math problem. This is someone who's had strong statements about race in America, she's had strong feelings about how she's been treated by whites. ... This really is a unique individual and so many of the issues and controversies that swirl around her might not pertain to every black woman who was going be a potential first lady, but it does apply to her."

FOXNews.com's Judson Berger and The Associated Press contributed to this report.