Paid leave has officially become a campaign issue for both parties.

Senator Marco Rubio on Friday became the first Republican presidential candidate to detail a plan for providing paid leave to workers who need time off to care for family members. It had, up to then, been a Democratic issue. Hillary Rodham Clinton, Bernie Sanders and Martin O’Malley have each made paid leave legislation a part of their campaigns.

The key difference: The typical Democratic approach would have the government require and operate a paid leave program, while Mr. Rubio advocates giving tax incentives so businesses offer it.

Presidential candidates are searching for policies to address challenges for working families, lift middle-class living standards and appeal to female voters. Paid leave is popular among voters: 80 percent of Americans are in favor of requiring companies to provide paid family leave, according to a June New York Times/CBS News poll.

The debate over the two approaches centers on how many people paid leave will cover and whether companies, left to their own devices, will decide to offer the benefit. Particular attention is focused on low-income women, who are less likely to have the opportunity to work at companies that offer paid leave, and are more likely to fall into poverty after a birth or illness.