In her first weeks in the White House, Mrs. Obama has been the gracious hostess and loyal spouse, welcoming visitors to the Executive Mansion and accompanying President Obama to a prayer breakfast and to a charter school to read to second graders. But in a departure from her predecessor, Mrs. Obama has also begun promoting bills that support her husband’s policy priorities.

Last month, Mrs. Obama celebrated the enacting of a pay-equity law with a reception for women’s advocates at the White House. Last week, she supported the economic stimulus bill on her visit to the housing agency and another to the Department of Education....

“She went to some lengths to say she was going to be first mom in chief,” Myra Gutin, a scholar of first ladies at Rider University in New Jersey, said of Mrs. Obama. “I don’t think we ever really imagined her edging toward public policy like this. It’s not like she’s making public policy. But it’s a little less neutral than some of the other things she’s talked about focusing on.”

Marcia D. Greenberger, co-president of the National Women’s Law Center here, countered that Mrs. Obama was successfully balancing her ceremonial role as first lady, her role as a mother and her keen interest in public policy.

“It seems like a combination of responsibilities that fit very naturally with who she is,” said Ms. Greenberger, who attended the signing of the pay-equity law at the White House. “You don’t have a sense that being a mom and being human and being able to understand everybody’s daily struggles has to come at the expense of her intelligence, her expertise and her understanding of the issues.”