“More broadly in the country, obviously there’s been more of a discussion about income inequality, wages and benefits,” said Bradford L. Smith, general counsel of Microsoft, which said in March that it would require many of its contract workers to receive 15 paid sick and vacation days. “In this area of paid time off, we’ve concluded that it’s not just good for people, but good for business.”

Advocates say they see an opening for a federal policy. “We’ve seen a dramatic shift in the last 12 months,” said Sarah Jane Glynn, director of women’s economic policy at the Center for American Progress. “For things that seemed a long shot then, the landscape looks completely different now.” As recently as one year ago, Mrs. Clinton said that while she thought paid leave was “unfinished business,” she did not think it was time for a federal law because “I don’t think, politically, we could get it now.”

Proponents generally fight for two types of paid leave: sick leave, for when employees or their children are temporarily ill, and family leave, for when employees need to care for a baby or a seriously ill family member. Polls show that the vast majority of Americans support both. Eight-five percent are in favor of requiring employers to offer paid sick leave, and 80 percent support paid family leave, according to a recent New York Times/CBS News poll.

The United States is the only industrialized country that doesn’t provide workers with any sort of paid leave as part of government policy. The Family and Medical Leave Act, which President Bill Clinton signed on his 17th day in office in 1993, gives about half of all workers 12 weeks of unpaid leave for a serious health condition, a birth or an ailing family member.

Now that a majority of women work, research suggests that the lack of leave policies hurts aspects of the American economy, especially by reducing the chances that women will continue working when faced with a new family situation. Low-income women, in particular, are less likely to work at jobs that offer leave and more likely to fall into poverty after a birth or illness.