Newswise — When First Ladies or candidates' wives speak, they walk a fine line. Their first job is to humanize their candidate, who many voters only know through attack ads or debates. Their power comes from the personal; we voters assume they will tell us something about his character, his morality--something real. Political wives are above the dirty business of politics, floating above the fray, buoyed by love.

Floating above politics, of course, is the perfect place to talk politics. Radiating charisma, Michelle Obama’s speech at the Democratic National Convention was a textbook example, even down to her protestation that for her and for the president, "these issues aren’t political – they’re personal."

Unlike Ann Romney, Michelle Obama did not have to make Barack Obama more than a face on a poster, even an iconic one. Americans know Barack Obama already because he is the incumbent and he has a pretty good handle on the charisma thing himself.

A clue might lie in the excessive "momminess" of the moment. Moms are everywhere in political conventions, real and rhetorical. Mrs. Obama began and ended her speech with her maternal role; she and others repeated the famous "mom-in-chief" line. She was even introduced by a military mother of five children, four of whom are actively serving. Nowhere was it mentioned that Michelle Obama is also a professional woman, someone who took the SATs and the LSATs, who held a job and managed a career, someone who wrote her speech herself. Herself.

But perhaps that "Mommy talk" was the point. In her address, Michelle Obama was participating in a centuries-old, very American tradition. Since the start of the republic, women have been called upon to "cover" the exercise of power with a peculiarly feminine language of love and motherhood. From the beginning of the United States, this "language of love" transcended party lines and in the rhetorical space it created, people from both sides of the aisle came together to politic.

With this (seemingly) apolitical language of love, Michelle Obama was extending a hand to people who would never be found at a DNC event — independent voters and even old-guard Republicans who, while publicly supportive of Romney, are privately appalled at having to vote a party line in which they have lost faith.

To be sure, some of what Michelle Obama talked about was calculated to bring the DNCers to their feet, as when she declared that her husband "believes that women are more than capable of making our own choices about our bodies and our health care" and the two mentions of marriage equality. It doesn't get more radical than women's bodies and gay people.

But these mentions and all her "policy" talk, including a defense of health care, came well into the body of the speech, cocooned by tales of parenting and being parented and values on which we all agree: opportunity, hard work, and the American dream. In fact, the whole speech was framed as an answer to her 2008 concern about the effect of the presidency on their two girls. (Deciding that having their father as president for four more years was the best thing for them was a nice rhetorical twist.)

The payoff to Mrs. Obama's nearly 30-minute speech was when she was talking about what she loves in her husband, declaring: "I love that for Barack, there is no such thing as 'us' and 'them' – he doesn’t care whether you’re a Democrat, a Republican, or none of the above … he knows that we all love our country … and he’s always ready to listen to good ideas … he’s always looking for the very best in everyone he meets."

Mrs. Obama’s speech was an invitation to those outside to come on in. As she waved and smiled, she seemed to say, "There is a place at our table for you. Maybe you don't want to stay forever, but maybe sit for a little while. Like four more years."

Catherine Allgor is a Professor of History at the University of California at Riverside and an advisor to the National Women's History Museum. Her latest book is: The Queen of America: Mary Cutts's Life of Dolley Madison (University of Virginia Press, 2012).